Anxious/avoidant

Hi Sam, I'm still getting over my ex who is definitely avoidant but I am not yet sure if he is fearful or dismissing, I assume dismissing but there are clues he might be fearful. True fearfuls are slightly rare but they do exist.
I myself took a lot of strength from attachment theory in my recovery. I have read attached over and over to gain acceptance of my own bad behavior in the relationship and why I felt so compelled to act in ways I would never have done outside of the context of my relationship. It also helped me realize why my ex acted the way he did which made me take the behavior less personally. Reading about the anxious avoidant trap helped me to understand why things never worked no matter how hard I tried because our natures inevitably didn't cooperate well. It also made me hopeful that relationships aren't typically the way I experienced my own.
I've read about avoidants to gain sympathy for my ex but to also make me realize that as much as I love my ex, an avoidant is not healthy for me and probably never will be.
I'm a scientist so this may be a more accessible strategy for me than for others.
Forgive yourself. Without knowing attachment theory it is almost impossible to understand the situation you were in.
Know that the relationship doesn't say anything about you. You didn't deserve to be treated the way you were, you just had a partner incapable of seeing how the way they treated you was unacceptable because they had needs that were so different from your own.
Try to model a secure person, after four years it is very possible your attachment style may have changed to an insecure style, but attachment styles go all the way to the neurobiological level. Your brain can almost certainly revert back to secure if you can internalize secure thoughts.
Do something that helps your self esteem. And something that improves your opinion of others. Maybe it's the gym, a new wardrobe, a new charity to volunteer at. Figure out how to self sooth again and don't let this relationship change how you feel about yourself, others, or relationships.
Finally, learn how to identify and thereby avoid avoidants. This will make you confident you have the tools to take care of yourself and be sure you don't end up in this situation again.

Best of luck.