I get knocked down...

but I get up again. That's part of the postdoc experience. Your self-esteem will get mangled, masticated and spat out. Then, you get to take the spitball (with little pieces of self-esteem in it) and rebuild it into a rudimentary sense of self-worth. If you do this enough times over, you attain a certain level of confidence in what you're doing. If you can't handle these facts, stick to looking at spreadsheets and adding columns.