I'm in that place where I'm blaming myself for failure, sometimes countering it with "but she did that and that, she wasnt ok aswell". My question is, how do I find healthy balance in it instead of playing blame game in my mind? How does it feel?
That is the start of you finding the healthy balance. Being able to practice the "wise mind" which there is a great article on here. It's just going to take practice. It won't be an overnight change. But rest assured, your example above shows that you are getting to the place of a healthy balance. I believe one day there will be a time when you think those things but don't have such an emotional charge or feeling to it. It will just be what it was and that will be okay.
Congrats on 6 months NC. Honestly, I don't think I'll ever wish my ex a happy birthday. It would serve no purpose other than to hurt me.