Can you figure intent into your consideration of moral peril? If you don't intend to cause harm... and if you cannot avoid causing harm... and so on.

Hello Johan, I can see why you might be apprehensive, but I personally wouldn't worry too much. I think Chris has posed a few good questions/inquiries above with an important factor being your intent. With regards to intent: if you're familiar with the famous "Trolley Problem" that's taught in philosophy/ethics courses, then this article may be very interesting and even slightly surprising to you: https://www.lionsroar.com/how-would-a-buddhist-monk-solve-the-classic-trolley-problem/

Another thought as there have been a few such questions raised on this board: the killing of others is simply our karma. Even if you eat an organic, vegan diet, bugs probably died as a result of cultivating crops and shipping them. Who knows? Maybe the long-haul vehicle hit a deer or racoon on the way to the super market alongside the many bugs dying on the windshield. There is blood on our hands no matter what, unfortunately. That said, we should not be complacent and ignore suffering or the death of others and we should try to minimize it, but to some extent it is unavoidable. 

A last thought: grass is pretty cushy & layered and most bugs have exoskeletons which can protect them. I honestly don't think that you'd be killing many bugs (if any at all) just by walking through the grass. Usually people have to twist their foot back and forth if they step on a bug that they intend to kill since these creatures are so resilient.
I have also been to retreat centers where there were paths for walking meditation in the grass so if the center was okay with providing these areas for walking, then I was probably in the clear morally. 

It's good to show concern as long as it's a genuinely compassionate response, of course. That said, you're doing a good thing by being on retreat which can help ease the suffering of yourself and others. Don't be too hard on yourself and just focus on good practice. Best wishes! 

Going off the last poster, if you were ok doing it barefoot, you would be even safer. And you would connect with nature more.

Hopefully you can learn to see that this vow was intended to support practice. Imagine monks walking in the jungle forest -- are they ever going to truly not step on anything? But also notice how the intention to not kills sharpens your attention and sensitivity -- that's the point. Also notice how your awareness of your own neurotic patters are seen forming around the vow -- that's the point, too. Find the middle path between ignoring the vow and obsessing over the vow. Use it to support your practice.<br /><br /> 

I think you are making a mountain out of a molehill. It is most likely your subconscious trying to avoid the real work of letting go of real attachments and aversions. It's a lot easier to worry about killing insects than to let go of your attachments to your body, your life, your job, money and the comforts it provides, your family and friends, and your posessions like your car and your house etc. 

You want to walk on the pavement to spare the insecets, but would you quit your job, risk your life, or give up your life's savings and your car to save them?

It is not the insects dying that is the problem. The problem is your own death.

Most people don't want to let go. Yet they think they want to wake up. They want to have their cake and eat it too.

Thank you all for the replies, very useful and interesting feedback. Funny how the path brings up "obstacles" that one wouldnt think of. I will take your advice and further investigate my patterns.

Yup, and those obstacles are great --- they are what teach us. So no need to get depressed or worried about being imperfect and making mistakes. That's all part of how we develop beyond where we currently are.

Like a baby learning to walk, it's going to fall on it's butt many many many many times.   But it's going to walk, heck it's going to run! 

With meditation, our internal wisdom slowly learns what works and what doesn't. It's mostly learning to neither ignore or indulge our emotions and thoughts...  and a lot of the time the lesson is to "not make a big deal" of things --- simply learning how to get out of our own way.