Practice vs league or competition play!
I watch players hit amazing shots in practice but in a tournament have real problems hitting any shot. I have learned you have to account for the difference between practice and competitive play. In practice you have to push yourself and be unkind to yourself. Do not be happy with winners, but do be happy with perfect shots.
Do not be happy winning a game on an opponent’s unforced error but do be happy about hitting a perfect shot to win that practice game.
Do not avoid the miserable cheaters of your club, but embrace playing them so they heighten the nerves in practice. I used to play one of the biggest cheaters in town and he won most practice matches but only beat me once out of 10 times in a tournament. Why? I had a ref to keep him from stealing all the calls like he did in practice.
I discovered in practice I shot from the backcourt more than in a tournament. My shot selection in competition changed dramatically. The reason for that was to get the opponent back of course and to work from back court in practice. I tried to be mentally tough on myself in practice but nice to myself in a tournament. Negative reinforcement made me work harder in practice, but hurt me in a tournament. So, + vibes only in competition!