Most of the time, when I paint, I start with a sketch. Some far-distant idea that may or may not evolve, but it gets into my sketchbook to give me something solid to mull over. A painting I did called "The Littlest Angel" started this way.
A simple idea, a thought, a brief sketch.
Then, a more detailed sketch with some color, to give me a more broad idea of what I hope to accomplish (although it seldom looks the same when the work is finished!)
Then, I transfer my idea to the final support, a canvas or paper, or wood. But I am always making changes along the way, not only in the subject but in the background as well.
Then, there is the final decision, after I have looked at it awhile, after I have decided it's finished, then decided it's not finished, after I think I don't like this, or don't like that, or need to change something. And sometimes the changes are a long time coming, and it really turns into a "remake" of a painting. So this now is the final work of "The Littlest Angel". I didn't like the cartooney faces, so I changed them. I didn't like the wings, so I added some gold leaf. A little this and that, and now I will consider this a finished painting. Finally!
And each time I finish a painting, I think..."gosh, I could have done better". Are you that way at all?