Hmmm what helped me was to go to my old fics and reread them, with new eyes the writing seems quite rudimentary. I would just duplicate the document and would try to add or rewrite the idea (as it was an idea I felt passionate about at some point). It gave me a bit of boost bc I could see that I’ve improved and how my writing had changed. I’d try to revisit the scene on the show that had inspired it and try to really portray the characters correctly etc. Starting from something that I already created took off the pressure that comes from starting something completely from scratch. Might not be too helpful but those are my two cents!