I think everyone at one point or another experiences this. When it happens to me, I take a day or two off and completely remove myself from any sort of dancing. I distract myself by going to the beach, movies, out with friends, or whatever just to clear my mind. Then I can go back fresh. I reevaluate what I am doing and remember why I started dancing- because I enjoy it so much. I usually watch some videos of old comps or some dance movie to put myself in a good mood and then when I practice, I do so by myself and I forget about choreography/technique and just dance. Its fun to just mess around and get whatever negativity out of your system. Then, I can refocus and go back to technique, choreography, etc putting myself 100% into my dancing.