I've been painting since childhood and somehow I only realized this in the last few years. A painting can only be a failure if you give up on it. Figure out what's not working and change it until you begin to love it. Areas can be painted over. Colors can be adjusted or changed. Don't approach it as a "paint by numbers " process. Approach it organically. You are never locked into anything . Initially just make sure the composition is strong. Everything else can be changed.

Walk away for a day or two, come back and you will likely see exactly why it’s not working then give it another go. If the next try doesn’t work start over. It’s not really a time thing.