Every day is a different day. For me, today was a bad day....

Every day is a different day. For me, today was a bad day. Today, I was warming up and it (the balls) were not so fast like before like it was on Monday or yesterday. I tried topspin, anything just to win but I can?t. I just said to my coach, ?I can?t do anything.? I am happy it didn?t happen in the Grand Slam, in the U.S. Open.