I like hard things. Most of what I do is going "the hard way" so it's just natural for me to push through. For example, I taught myself to code using only the internet as a resource at night after work before changing careers to do it full time. People told me getting a tattoo on the ribs was one of the mores painful spots, so that's where I went first.
I guess I get the thrill out of pushing myself and succeeding -- or learning from my failures.