Don't put yourself in a mental rut by saying you've gotten worse because you aren't performing as well. Generally speaking, when you believe you've gotten worse, you'll play worse. Somewhat of a self-fulfilling prophecy.
I remember having some good days where the stars aligned, and I'd go god-mode and perform at my best for a day. Then I come back the next day, and suddenly I've 'gotten worse' at the game and it'd demotivate me. Now I just acknowledge I had a great session yesterday then continue with my play session.
Also, A good warm up can make a BIG difference, helps get you physically ready and mentally focused. I generally just play some easier/moderate songs with ScoreV2 HR RD when warming up.