I actually wrote an article about this. You can read that
over here.
I think the usefulness of having goals can't be overstated, for this exact reason. Music is such an abstract art form that it's generally very difficult to measure one's progress.
When I was a student, the ultimate goal was full-time employment as a player. It's one of the least ambiguous goals I could think of. The road to that particular goal was paved with much smaller mini-objectives and a few side quests. Medium-term goals were things like "
get accepted to summer festival X" or "
have a lesson with Professor Y" or "
sub with Symphony Z". Those goals get reduced to "
learn such-and-such piece" which reduces further to "
get page 33 up to tempo 44." Eventually you're looking at micro-goals like "
connect note A into note B flawlessly."
The vast majority of your time will be spent on those micro-goals. It's good to look up ahead from time to time to make sure you're still going in the right direction. Just don't get lost in the clouds.