@IvyNightShade (for some reason I cannot quote you): I totally understand how you feel. New experiences can sometimes be very intimidating and it can be tempting to somehow talk yourself out of them.
The best suggestion I have for you is to invest in new things in a way that makes it harder for you to back out last minute because of anxiety. Here's an example: You know that feeling you get in your stomach right before the roller coaster goes down? That anxiety of knowing something's about to happen, and yet, you're strapped in, there's no where to go, so you HAVE to go through with it. That's how I would think about trying new things, at least until you can break the habit of over-thinking.
At the end of the day, you have to get yourself into the mindset that by not trying, you're losing by default. On the other hand, if you try something, and it goes horribly, then you're at least one more hobby/activity/interest closer to finding something that you do like. And remember, it's totally okay to not be good at something or dislike it! Don't look at it as failure or something to be upset/ashamed about.
"Don't be afraid to give up the good and go for the great."