I'm sorry for the betrayal you went through but know this happens to so many people. What you need to know is that people want what they don't have and then when they get bored of an experience or person, that tolerance makes them want to look for something else.

The solution is to self-parent by taking the love you gave to someone else and giving it to yourself. You do this by imagining your inner child and then asking "what is in the best interest of my inner child?" This way you can create concern for yourself and parent yourself with healthy protective actions. Over time your love for yourself will make you more attractive and you'll find partners who also love themselves as they are. It creates a security for yourself and makes better relationships.

Really in some cases people should grieve for a period but thank their lucky stars that the abusive person is gone. The new person who gets the attention may feel good for a while but when the ennui sets in with the abuser then the same thing could happen to this new partner.

Self-development should be for your own enjoyment and pleasuring yourself means you have a self and when you connect with someone else you can apply boundaries because you actually have something worth taking care of. By applying punishments like withdrawing your support and attention when there's abuse means you are not an inanimate object. You respect yourself and if people want to be around you then they have to respect you as well.

Relationships are difficult because you have to be available part of the time but not so available that there's boredom. You also have to have dreams and goals for yourself that are independent from romantic relationships so that you maintain a momentum of success or progress (even small successes are enough) to keep a partner interested in you.

Keep up the self-development. As you act on what you are reading, each action conditions you further on your goals. Trying to make each action a support for your goal gives you that momentum. I've seen people in devastating divorces and after years of the fear of making a new committment, they found a better person. This was because they were more cautious and looked at the new partner with a view to how they were treated and noticed red flags faster.

I have found Toni Burkhart's books, especially How to be Sick, to be very helpful. I have health issues of my own, and I sympathize.

As corny as it may sound, love really is the answer (echoing Richard here). It is indeed possible to love oneself from the inside out and the outside in. Compassion for your own suffering is a good place to begin. As you learn to cherish this being (you) with your whole heart, you will find the apparent crap shoot of this life to be less significant. Waking up helps tremendously as well. One's perspective changes drastically. But in the meantime, self-love, properly understood.