Whats up guys. Havent been posting here since 2 1/2 years ago so it feels good to be back. Anway on to my question--idk if anyone experiences this, but sometimes I'll walk on court and be crushing balls; precise and powerful rips. Other times, I'll be hitting and it'll feel like I'm using a block of wood and it makes it hard to generate pace and build up consistency. Assuming the strings aren't dead, what can attribute to the differences in response from the stringbed. Sometimes I'll feel like I'm playing at a 6.0 level and flash forward a few more days and it'll be very low quality tennis, because of the response of my racket.