This can really be hardwired, a part of you that you are born with---(I remember, and still see though they are grown, being amazed at the personalities my children came out of the womb with that have stayed with them through life...we are not born a blank slate)--I also think being able to acknowledge this part of you is a great step, especially if you can let others know "this is me", and smile.
All I can really think of doing is creating a space within which you are "allowed" to be silly, not the "best" etc. (or in which you are allowed to laugh---bet there is a stand up comic out there with your expectations of self that has learned how to use the pain for humor...) I guess I am thinking you might take up doing something a few hours a week that you put apart from the you so serious...
(Haven't tried it but I hear, really, that laughing yoga is a stress-buster---
or a "sport" you can fall down in and laugh about...
You need, methinks, a place to PLAY for a few hours...