Yup, been there. Definitely personal projects outside of the daily work grind and stepping outside your comfort zone. Also, taking a break from learning tools and diving into design, art and strategy. If you're interested in getting more into the art direction side, I highly recommend Carey's latest video: http://www.division05.com/007-style-strategy/
If you want to share your work we can give you pointers on where your improvement opportunities are, finding a mentor or support network that challenges you to improve is also great.
Getting back into things like typography, drawing, creating stories helped fuel learning the tools part again for me, but totally unrelated interests like Aleksey mentioned are great too. Get out of your rut and try and get a bit of wonderment back