Please stop beating yourself up for walking away from someone who was not "there" for you despite all the effort you put into being "there" for them. Often we feel pain and can feel guilty for feeling pain when it's really not fair to ourselves to carry that kind of guilt. This individual told you he did not want a relationship, that meant he was never interested in being "there" for you and he WAS NOT there for you but constantly expected you to be his emotional dumping ground.

Maybe he remembered your birthday, but that was not for you, instead it was an invitation to allow him to pull you back into being his emotional dumping ground. I believe you gave him the kind of caring and attention YOU wanted yourself. The problem in this situation is he was not EVER interested in giving to you that way.

You need to learn to believe someone when they show disinterest or lack of genuine caring. Instead seek people who can actually appreciate you the way you deserve.