Morning, Afternoon, or Night?
I have a student I used to coach in the afternoon after school. He'd always be tired, with little interest. His mom and I decided to try something, and we tried coaching him in the morning one time. Instant energy! He was suddenly enthused and interested. Now we're rearranging his practice to take this into account. We may also try him out later at night, when he's apparently energetic again. (I also suggested a nap after school - perhaps that'll bring his energy back faster.)
I've also faced this. For years I struggled to play in the afternoons - like the kid above, I was always tired during that time. At night, however, I'd come alive. But I've done so much coaching and playing in the afternoons now that my biorhythms have changed. Now I'm energetic in the afternoon, a bit less so at night, and tired if I have to coach in the morning. (Mornings are for writing, not table tennis, in Larryworld.)
Most players play at night, and probably are at their most energetic at that time. But when a tournament comes around, most play is in the morning or afternoon. I know this affects some players; how about you?
When we know the time of important events at big tournaments we sometimes have our local juniors train at that time to get used to it. (If it's in a different time zone, we take that into account.) It really helps. I remember a kid who had to play an 8PM match in Las Vegas, and he was still on Eastern time - so it was 11PM for him, and he was half asleep and yawning before he played. I sent him into the bathroom to splash cold water on his face (this helps), but he literally yawned throughout the match, played poorly, and lost.