Azrael is right when he says that you need to "learn how to learn". Study yourself and what you want to achieve with this instrument, and work out a practice plan to achieve it.

A thoughtfull and pragmatic practice routine WILL produce results. But remember to have fun! Designate a portion of your practice time for jamming or just messing around, and then get down to business. Do your excercises and what not as if its math homework, very structured and disciplined. And once you're done them, take a fifteen minute break and just have fun. Then back to excercises.

Obviously that's just a suggestion. You need to find out YOUR perfect practice schedule, tailored only for you and designed to get you where you want in terms of playing the guitar.