Well, it's a bit unrealistic to think one will be proud of every piece they make. You do have a point regarding not being ashamed of one's work, though.
We are starting to reach semantics-level of arguments here. My final thoughts:
1) Don't just "draw for fun" if you want to be a professional. Challenge yourself.
2) Don't just do intense studies for 15 hours a day unless you sincerely enjoy it and can actually do it on a consistent basis without getting burnt out (rare).
3) The whole point of being a professional artist is to do something you actually enjoy while getting paid, and your journey should also reflect that. So, draw things you can see yourself drawing for hours on end every weekday.
I think these are quite agreeable.