I saw this on a poster recently and really liked it. It's an excerpt by Ira Glass. I believe it is originally from a speech (you can find it on youtube).
What nobody tells people who are beginners - and I really wish someone had told me - is that all of us who do creative work get into it because we have good taste. but there is this gap. For the first couple of years you make stuff, it's just not that good. It's trying to be good, it has potential, but it's not. But your taste - the thing that got you into the game - is still killer. And your taste is why your work disappoints you. A lot of people never get past this phone; they quit. Most people I know who do interesting, creative work went through years of this. We know out work doesn't have this special thing that we want it to have. We all go through this. And if you are just starting out or you are still in this phase, you gotta know that it's normal and the most important thing you can do is a lot of work. Put yourself on a deadline so that every week you finish one piece. It's only by going through a volume of work that you will close the gap, and your work will be as good as your ambitions. And I took longer to figure out how to do this an anyone I've ever met. It's going to take a while. It's normal to take a while. You just gotta fight your way through.