Don't think of it as "practicing." Think of it as "spending time with the instrument." There are sort of two ways of "practicing": the wrong way and the right way. The wrong way is sort of watching the clock and sawing away for a certain number of minutes. The right way is to forget the clock and actually PLAY the instrument with intense focus. You should never "practice" for more than 20 minutes at a stretch. If you can do two, three, or more such "practice" sessions a day, you will get good at playing the instrument. But never underestimate the value of "practicing" even just for 10 minutes. If you're really listening, your muscles and musicianship will benefit. Having even a general idea of both short-term and long-term goals is helpful. Keep track of what you're doing, and certainly what is required from the teacher every week (if you have a teacher). One of the best books you can get on this is Barry Green'