Well, I understand what you're saying related to friendships, and to be honest, it sounds like a far more complex situation than what has been laid out here in your relatively short post. Which is fine, you're not obligated to share, but what I'm getting at, is that in all of this what seems to be the core issue is that you lack friends and blame yourself on some level for this problem. While it could very well be something you've done to make it hard to keep friends around, it's rarely entirely our own fault. In almost every person's life, there are instances where we've "burned bridges" with people for no good reason where other situations called for the breaking up of a relationship. I would not lump all of them into one thing, like being something that you do.

In this case I'm not so sure about the co worker but with the ex best friend, I can see why it was a good thing to cut off ties. With that person, I am not sure why you'd even miss them or have any regrets if indeed they were toxic and hurtful. Just move on from that one and accept that even though all people have some good in them, not all of them are good for us.

From this and other posts what I've gathered is that you're one that has a problem with self image and confidence socially. If any part of your lack of friends is on your shoulders I would place it squarely on these traits or lack thereof. I don't know if you're a self help person or someone to find help via a therapist but either way I think this issue with your self is the key to building a better social life.