I sometimes go through the same thing. I'm an engineer and a dancer. I don't always feel pretty on the floor. When I watch videos of myself I cringe. Most of the time I feel clumsy and slow while other times I feel great but my dancing is horrid. The only way I get through these slump periods is to look in the mirror and tell myself "you are good at this" or "you're better than this and you know it" whatever the situation calls for. Sometimes a break from dancing is the only thing that helps...with a large pizza. Then I'm back at my next lesson refreshed ready to shake what my mama gave me, and work off that pizza I just ate. Maybe that helps.