A basic truth about creating (or teaching or nursing or painting) is that you'll only get better if you keep at it. Longterm practice breeds longterm expertise.
It's unfortunate for twelve-year-olds learning to play the piano and seventy-year-olds who've never thrown a baseball—but it's true. You don't get to be an expert without perseverance, and hours and hours of saying no to EVERYTHING so you can get good at one thing.
This ability to keep going requires keeping your mentality healthy, which takes intentionality and grit.
What if someone tells you that you're not really great at this, you're not going to make a longterm difference, and your best work is something else—like labelling cans?
There's a whole lot of things you can do: weep, yell, slam doors, break bottles, lock yourself in your room, mope, try harder, got more opinions, set the painting on fire and try again.
But you must not stop trying.
Because if you do, your work won't make a difference.
Because nobody ever changed anything by quitting.