Sometimes after I accomplish something, I start worrying that now expectations will be much higher and I will get in over my head. It is like I find something else to worry about instead of enjoying the accomplishment.

I also think people that were told in their past that their accomplishments were never 'good enough' have trouble enjoying success because they hear (subconsciously) those voices from the past that told them it still isn't good enough. I am not sure that applies to you.