What motivates you to write?

When I was in high school, I was writing all the time. I have at least 70 "stories" (not sure what to call them), but then I went to a creative writing class. The teacher, an author, told me I wasn't good enough to be a writer. I stopped writing after that. It's been about ten years (god I'm old) and I had an idea for a story. I'm really excited about it (I have a cover design and everything), but I'm just so nervous to write. I got one and a half chapters done, but I can't bring myself to continue in fear of it being bad. I really want to get it finished and possibly published, but I can't do that until I actually work on it. So, as the title says, how do you get motivated to write, or over a fear of writing? Thanks in advance!

Edit: I have a friend who is looking over as I write, like an editor. She's been so helpful, but also supportive. Someone in the comments made me realise that I'm writing a story about something I have no experience in and that might be part of it, as well as a different POV (used to do first person, now doing third). As a little background, this character only came to be because I wanted to make a paladin for dungeons and dragons. The more I fleshed him out, the more I thought his story would be more interesting as a book, also because I wanted to figure out how he reacts to certain things and know that can't happen correctly at a table. I'm really interested to see how he gets from point a to point b (I have the climax planned out) but it's always the struggle on getting to the climax of the story. I also thought it would be a good story that others would want to read (this is 100% a book my dad would have read). I'm definitely gonna keep all y'alls advice in mind!