I notice many players have wrist issues and a simple thing, I do it often because of weight lifting, stretch out before you do the work out!
Rotate the wrist all the way around, much like folks do stretching their calf. Then reverse it and flip it over stretch the other side, do this for both hands before you play. I do this against a wall or post, applying pressure and tension to stretch the muscles out, generally at least 10 sec per position. Also, if you push against the tension, you will get a better stretch(active stretching).
This will help the muscles a considerable amount and reduce fatigue, which means better, more, and effective playing
Note: you can similar routines for the fingers(say sore 2-3 picking fingers or that poor slap happy thumb)
Seriously though, try this simple sometimes so obvious that we forget about it, pre playing stretch. You should see better playing, longer playing, less pain and suffering.
Regards,
tom