I always want to keep revising things which leads me to never finishing at best and actively ruining something at worst. Also, I'm often put into situations where I need to submit the best of my work (like for contests, publications, or resumes) but I never know what the strongest pieces of my portfolio are. How do I figure that out?
that's impossible too, if you are supposed to be the one who is in charge of making them good. once the thing is done, it would be too late to decide if it's good