For me it was advice from Dan Harmon: “Don’t try to prove you’re a good writer, you’ll never write anything. Try to prove you’re a bad writer and you’ll write everything.” Not perfect advice but it really does help me write when I’m being overly critical of my ideas.
I never received this advice, but I feel like it would’ve helped me get into writing well before I actually did. It’s okay not to finish. The 50 google docs you have all show your work, how you’re advancing your skills and expressing yourself more and more in each response. I used to only be able to write a few sentences before quitting, but now I go much longer.
Also, length doesn’t matter. I used to constantly try to set goals for how much I’d write in far too short a period. This may be useful for some people, but for me I just got distracted, obsessed with reaching my unachievable goal, and it was far less then helpful.