Here's a thought to keep yourself in check while practicing your instrument. Record yourself for a 30-45
minute stretch. What kind of practice techniques do you have? Do you practice with a specific goal in mind
and work through each phrase with mental focus? or do you noodle around  without every clearly grasping
the music in front of you? Are you relying on muscle memory? or something more substantial? Is what you're
doing giving you the results you want? If not, maybe it's time for a change in your approach.

"The right kind of practice is not a matter of hours. Practice should 
represent the utmost concentration of brain. It is better to play with 
concentration for two hours than to practice eight without. I should say 
that four hours would be a good maximum practice time—I never ask 
more of my pupils—and that during each minute of the time the brain be 
as active as the fingers.” 
~Leopold Auer