The suggestions given already are good. Like they said, shake up your routine. I sometimes start using only cables for awhile; no free weights. The key is to do something.
There is also something called overtraining. It's when you train too much or don't give your body enough rest. You might experience some loss in strength or even feel like you are in a funk. I have experienced it. Not fun.
I cut back going to the gym and substituted activities that kept me active, but allowed my body to heal. I walked the neighborhood or to the store and that counted as my gym time. If I did hit the gym it was for some cardio, stretching, or even some light weight training, but i kept it to just 30 minutes.