My only fear is that I won't be able to finish producing all the stories I intend to make before I die. I actively combat that fear by aggressively working on my comics. My only goal is to make them well and get them out there. After that, who cares? I'm already working on the next thing.
Everything else, how big it gets, what people see in it or do with it in fanon, the pressures others might try to place on me to change should I get well known...that's all outside by locus of control and idk if it will even happen. So even if it gives me some level of trepidation, I figure if it happens, I'll deal with it.
The cure to fear is action made to overcome it after all.