Here are a few practical tips on what you can do in order to bring your motivation back to the high level:
Go back to the reasons why you practice guitar. It is very important to be aware of why exactly you practice your instrument. Every activity that requires huge investment of resources needs to be backed by reasons strong enough to follow through with it. It is good to have them written down on paper in a visible place so you are more aware of them. What is the reason you practice guitar? What was the original motivation to start doing it? How would you feel if you have accomplished your goals?
Get inspired with something new. The sources may be both musical and non-musical. Personally, I constantly seek for new artists and bands to be exposed to new ideas as often as possible. I also like to read interesting books, watch movies and visit art exhibitions.
Reevaluate your approach. Is the way you practice the most efficient? The reason of you feeling overwhelmed might be that you try to do too many things than you can handle. I`m sure that you may only need few tweaks to make it more enjoyable. Think of something you don't like practicing and it's hard for you to sit down and start working on it. If this thing is necessary to achieving your musical goals, come up with ways how you can make it more enjoyable and save yourself negative feelings while attempting to practicing it ineffectively.