Never complain and never explain.
Always desire to learn something useful.
Things do not happen. Things are made to happen.
If you think you can do it, you can.
If you've got a talent, protect it.
I can, therefore I am.
It's always too early to quit.
Quality is not an act, it is a habit.
To know oneself, one should assert oneself.
By failing to prepare, you are preparing to fail.
There's obviously nothing wrong with selling your art - only an idiot with a trust fund would tell you otherwise. But it's confusing to know how far you should take it.