There is a slang term used in the U.S. (usually by women): “the fuglies.” It refers to days or weeks when everything seems wrong with your appearance and you just can’t manage to look the way you want to. The term is also sometimes used to insult someone you find unpleasant to look at. The word’s etymology is profane.
In my experience, just about every painting goes through one or more fugly stages. There is a point where the painting, at least to the artist, is hideous and seems unredeemable. There is no point to continuing, because the painting is doomed. I’d post more work in progress shots, but the fuglies really bother me.
Unless you are prepared for the fuglies, they will destroy your ability to finish any painting. It takes a leap of faith to look at a work in progress, be revolted by what it looks like now, and believe that it has potential nonetheless. You have to believe that you can make it look right, even though right now you can’t stand to be in the same room with the thing. The more you’ve done it, and the more you can remind yourself that you’ve been able to get through this before, the easier it gets.
If you’re a beginner, it’s even worse. You may not yet have made a painting that looked anything like what you wanted it to, so it’s hard to keep working on what feels like a piece of junk from start to finish. That’s a leap of faith as well—faith in the idea that even if this painting is ugly, the next one will be less so. Take my word for it: if you keep at it, your work will get better.