today i played in a satellite tournament against an opponent who was about the same level as me. i was playing really good and normal. i won the first set 6-4 but after the first i collapsed. i couldnt focus at the ball at all and my eyesight was extremely bad which led to me making bad calls. it felt like my head was somewhere else. not only that but i was sooooo tired so fast and that is not something that happens to me because im fit. now im home and im still not feeling good, my head kind of hurts and i feel like throwing up. my question is what could be the problem? is it because i didnt eat anything, not even breakfast, before i went to the game?? or is it that i tried too hard and wasted all my energy in the first set? P.S. ive played longer games than this one so i was surprised when it happened to me.