I definitely know what you mean, I've been putting off doing a game jam myself for quite a while now because I also have trouble dealing with time limits. I think I only now decided to do it because I decided that even just joining up and trying my best, even if I didn't make it in time, was a victory worth celebrating. Learning all this stuff is hard and it takes a lot of time and patience. Even if you don't get to do this game jam, there will always be others to tackle. You got this!