It's Easy to be Self-Critical, but Hard to Turn Self-Critiicism to Advantage

Anyone can beat themselves up with a long list deficiencies. I do it all the time. Self-criticism is actually a powerful tool, if used right. The problem is that negativity is typically de-motivating, since it's hard to enjoy something that you know you are doing badly. If you aren't self-critical, though, it is hard to improve to the point that you can enjoy your writing. Complacency doesn't really get you anywhere either.

The trick is to develop self-criticism itself, the ability to evaluate your own writing and see where it needs to be changed,for example, as one of your special talents. To see that a sentence I've written is a piece of shit might be disappointing, but I can move from "this sentence is crappy, therefore I am a crappy writer" to "Boy, I am really good at finding these sentences in my own writing and fixing them before anyone else sees them." Or "I am really good at anticipating possible objections to my arguments."

As I've pointed out before, there is really no point in singling yourself out as particularly bad at things that almost nobody else is good at either. That is also a form of egoism.