For some of us, (no doubt it helps to be financially secure) we can have the confidence that what we're writing is not measured by whether an agent or publisher picks it up. I work every day to be a better writer than I was yesterday. That is my measure of success.
I'll be fine if when I finish my WIP it doesn't win the publisher lottery. I believe it's a good novel, not based on an unfounded belief I wrote something I think is great, but because I've worked for years (going on seven now I think) to learn how to be a better writer.
You have to invest in learning. That I believe, though some people are natural born writers who have learned the craft early in their lifetimes. If you have a story to tell and you think it's great, then invest the time to learn. When someone says 'filter words, show don't tell, you don't need to tell the reader twice, use stronger verbs' or whatever, invest the time to learn what they are talking about. That is so much more important than someone pontificating philosophical mantras that have nothing to do with how one learns to write.