Narcoleptic, I've been in that situation too and it's bad. The weird combo of negative/positive is actually worse in some ways than all negative, because you start to have hope that things aren't as bad as you think.

I hope you can find something better or figure out how to handle it. I'm starting to think that I want to just figure out how to get over this stuff, because I keep running into the same situations.

With regard to mistakes, I own them quickly and matter of factly and do not over apologize. If I screw something up, even something huge, I say 'I did that. Here's how we can fix it.' No massive apologizing or trashing myself in front of others.

I have been thinking more about what Hooligan said and will try to put that into play today, focusing on the value I add rather than insecure thoughts about the things I get wrong or don't know.