I like to write stories, and I want my stories to be consistent, so I build the worlds so that I can control how consistent they are... And then I keep building and keep building. It's not a bad problem to have - there are worse things to be addicted to.   I love culture and language, so these are my favorite parts of world building, but I do have trouble accepting that I can provide something less than perfect now and fix or perfect it later when I have more time and/or information... which is odd because I don't consider myself a perfectionist.