Hey Tim!
I'm not a parent, but I feel you in terms of balancing the merits of meditation with the realities of daily life, stresses and troubles, and feelings of coming short in terms of how you'd like to feel vs how you actually do feel.
Quick Q- what was your meditation practice like? Were you working with any framework, techniques, particular goals in mind? Just curious what led you here, and if you're familiar with stuff like vipassana/jhana, some of the core tenants of Buddhism, etc...
But basically, I feel you and I'll try to break down my own understanding and experience. In classic Buddhism, there's this notion of the three trainings
1. Morality/Virtues/Values-
How we approach our lives, the kinds of qualities and actions which we aspire to, our stance on what's right/wrong, the way we tend to our behavior and habits, etc... One way I could generalize this would be "life off-the-cushion" (life outside of meditation)
2. Concentration -
Generally speaking, the practice of focusing the mind, reeling the mind in, smoothing out and centering the mind, attaining and deepening focus, etc... more specifically, this branch also deals with the jhanas, states of progressive meditative absorbtion
3. Wisdom/Insight -
The practice of examining reality to understand its true nature, shining a light on the present moment to see more clearly what it consists of, looking to see the fundamental characteristics of all sensations, etc... this practice is vipassana, and is the practice said to lead to progressive stages of awakening, permanent changes to how reality is experienced.
Anyways, in this whole framework, the path of progress is often a balancing act between all these branches. I think it's great to attempt to be the best parent (or just human) you can be, trying to be positive, etc... However, it's worth mentioning that while ideals for morality/virtues and the relatively simple aim of concentration are generally straightforward, the third branch is not so clear. In our daily lives, we strive to be better, to act more skillfully, to cultivate positive mind states... In concentration, we learn to focus and abide in deepening, restful, pleasant meditative states. But insight practice is different in that the main goal is just to see the picture more clearly, to see what's actually going on in present experience, to bravely and skillfully confront reality where it's at in order to gain a better understanding of what makes up experience.
The progress of insight practice can be difficult (again not sure what your familiarity with these terms are, forgive me if it's stuff you already know), but it's also generally the one that can transform our relationship with reality and experience in a way the other two branches can't. Getting back to your original message, it's that idea of, what can be done when our best efforts to be the best we can still leave us feeling short, still leave us feeling feelings we don't want to feel? The general tenents of insight practice can be really helpful here!
Feeling good, feeling positive, cultivating the mental qualities we'd like to have is great and a good pursuit. But the reality is that we also get stressed, angry, tired, impatient, selfish, hurt, etc... these are also totally fundamental and natural parts of life, and I think skepticism that they can be eradicated completely is good! Why I bring it up, is that when faced with negative aspects of life, we can feel like we're slipping, our practice wasn't deep enough or somehow got thrown off, we're being bad, etc... but insight practice or at least it's general spirit can be really useful for dealing with this stuff.
As a general summary, insight practice consists of looking into experience and seeing the truth behind it, seeing the true nature of reality, seeing what it consists of, how it works, that kind of thing... it's not so concerned with generating positive mental states as it is with deeper acceptance, maturity, and scrutiny into what makes up reality. Thus, it can be very helpful in approaching things that are negative in nature. Feeling stressed or impatient? These are simply more qualities of the mind and body. It's not that you use this scrutiny to zap away the stress or get them to go away; more that in accepting that reality as "where it's at", you can develop a more positive relationship with your total experience, even the negative parts.
Positive and negative experiences are always coming and going, we like the positives and would like them to stay, we dislike the negatives and wish they weren't unpleasant. Nothing wrong with that at all! But in learning to confront reality where it's at, we slowly transform our relationship to experience, slowly learn to loosen the grip of positive/negative qualitites, learn to approach reality where it's at without holding too tightly or pushing it away. Importantly, the experiences that arise, positive or negative, are not "you". These sensations come and go, and as much as we identify with them, they are transient, exist and then pass. In insight practice we find that part of the problem is not in the content of positive/negative, but our own relationship with it. When we practice insight, we tune into a kind of distance and perspective, where we see experience more accurately, we don't identify with it as deeply, and we're more able to face both the positives and negatives with more maturity and balance. We're able to experience whatever we experience with more honesty, patience, wisdom, perspective, etc...
So again wrapping back to your original thoughts, maybe looking more into insight meditation could be useful! You don't need to be super concentrated or have a saint-like mentality to do, and whatever is happening in your experience is always completely valid fodder for the practice. You can notice feelings of stress, notice feelings of impatience, and have the presence to truly just sit with those, see them as they are, allow them to be felt, honor them as being part of the picture, and make it a goal to just watch them, watch the mind's reaction to them, watch the way so many sensations and mental states/emotions simply arise then vanish. Even just at the surface, it's fairly freeing in the sense that you don't have to be in an ideal mood or mind-state to do, you can simply rest in the fact that whatever is present is reality, reality is truth, and thus you can't really get it wrong by making a commitment to just watching it, accepting it, seeing it more closely, that kinda thing.
Said another way, a lot of people spend time meditating to cultivate positive states, to bring more positivity and focus into their lives, and expect a generally upward trajectory of peace and calm. This is not necessarily a huge problem, but can be opposed to the simple reality of negativity/pain/unwanted feelings and thoughts existing. Insight practice is useful in realizing even the negatives and tough stuff is still equally valid fodder for focusing on! You can see impatience, allow it to be where it's at, and learn to sit with it and examine it, not try to push it away, and eventually, you might find that even the negative stuff isn't as problematic as you thought. Meditation doesn't always have to be positive; sometimes we make huge strides by learning to bravely accept and honor the reality of what's happening, not just focus on the qualities we like or aspire to.
Anyways, I said a lot and this message is pretty big, but hopefully you'll find some of it useful or at least helpful for starting pointers for further conversations or things to look into. Basically, it sounds like you're doing great, and perhaps a good way to proceed could be to approach your stresses and difficult feelings not as backsliding or roadblocks, but as simply more valid experiences to examine, to allow them to be your practice instead of impediments to practice, etc... In the face of adversity, I've often felt my practice derailed. But in allowing that to be the case, I've found massive benefit in learning to simply sit with those feelings, look into their nature, meet reality where it's at, and gently let go of many of my ideals about what meditation should look like, how meditation should change me, gently challenge notions of how I ought to perfect myself, etc...
Hope this helps or inspires some degree of confidence, and happy parenting!
