A long time ago, one of my mentors said to me, "Ann Marie, don't ever go where you are not wanted". Now I understand after many years what he meant(RIP Mr. Roy Boyke). This insight has saved me a lot of pain an embarrassment both personally and professionally.
I'm sure you remember occasions where you may have been left out of being invited to a party. Maybe a group of colleagues decided to go out for an after work drink and you were not invited. Don't for a minute wish that you were, just tell yourself that it was not meant to be. By saying, "geez I feel bad because they don't want me around" sends a message to the universe that you are not good enough. Instead know that your place in this world has already been determined and you don't need to chase after anyone or anything.
I know only too well how it feels to be anxious abut a business deal after making a presentation. It's tempting to keep calling the organization you presented for even though you're getting signs that that they are not interested. Or the job interview that didn't seem to go anywhere. Then there is the ex-boyfriend or girl friend who dumped you but you keep calling. Oh I could go on and on but I think you get the idea by now.
It feels much better to just forget it and move on to other things. Trust me, it does a lot for your self esteem. Don't put yourself in a position to be rejected, it's just not worth it. So the next time someone closes a door in your face, say thank you and use it as motivation to do great things with your life.