Hey man, I can safely say practically all musicians have gone/will go through what you're feeling right now. There are a few things that could help. 1. Go through and listen to a few of the original songs that made you want to pickup your instrument. Maybe it's a super shreddy solo of Syn's, maybe it's a poppy Beatles tune that helped you get through a rough patch, or maybe it was a super tasty Billy Gibbons lick. Go back and listen to what convinced you to pickup the instrument. 2. Take a break for a couple of days and come back to your instrument. Some times we go through periods where we are playing up a storm regularly and you're learning a ton of helpful information from the school or another source and you end up getting burned out. It happens. If I'm not mistaken I remember seeing Papa Gates tweet a little while ago about not having picked up guitar in 3 months which I'm guessing it has been a while since he's taken that long of a break but sometimes it's needed. Take a couple days off, a week, hell a couple of weeks off. Come back to it and see how you feel about your instrument. Another method may be to try learning a technique that you haven't even though about adding to your arsenal. If you've been playing metal a lot and mainly tremolo, down, or just alternate pick the parts/songs/whatever maybe try working on your finger picking or crossover picking. Maybe you're not losing general motivation instead you're not getting as stimulated from improving your playing if you've been playing/doing the same thing for a while. Hopefully this helps dude!