Success can have a strange effect. It raises the bar for you. The merit of your accomplishments become relative to what you did yesterday. If you don't out-perform past results, you're failing. And if you're failing... then aren't you a failure?
I think we forget that failure is the default state. Which redefines success to be making any attempt at all. Like Edison said: "I have not failed. I've just found 10,000 ways that won't work."