Everything an artist does is useful. Every failure is a lesson learned, every exercise and job is practice. All you have to do is put in the time, and if you don’t you might get bitter but you have to accept that it’s your own fault. That’s hard. I know because that is my main problem. Just don’t add stress to your worries by comparing your progress to another artist’s. everyone works and learns at a different pace. Just do something and you will improve. The more you do, the more you improve and the faster you improve. Simple!