Why do I always get extremely nervous even though I'm doing what I love and am good at?

this is very normal and common. Our brains tend to overthink things even events that are familiar to us. for instance I consider myself a good public speaker however I realize every time I have to do a presentation I still panic and get anxiety prior to the event. However once I start to present the anxiety leaves. So try to figure out what makes you feel better prior to starting. Always remind yourself how the worst things you fear never come to pass! Pep talks you give yourself maybe very helpful as well. You got this!!! You are good at this remember!

I think that the nervousness can stem from a possible different reasons. In your head, you might be able to logically remind yourself that you're experienced and you enjoy the things that you're doing. However, depending on the activity that you're doing, especially if it's one that is performance centered, you might possibly be nervous because there are people who are watching you. For instance, I enjoy creating art and playing the piano. I love doing these things, and I know that I've built up skill and experience throughout the years. At the same time, there's still a sense of stage fright or nervousness that I experience when people are watching me. For me at least, I don't want to mess up or let the people around me down. And I don't want to suddenly be revealed as an "imposter" who has just been faking it this whole time. I'm not saying that this is exactly why you feel extremely nervous, but I'm just posing some possible explanations.