I figured I would put this up to help people and hopefully never experience what to go thru for that last few years!! Your wrists have alot of tendons and veins running through a very small space. Cross stitching makes you use the same motion over and over again. I did experience a repetitive injury and it took over 3 years to fix its self (well almost-- I'm still very careful with the one tendon that runs from between your thumb and straight down my arm-- it still gets sore time to time)
1- Never stitch with cold hands - try to warm them up first if you really want to stitch!!
2- Stretch before you stitch and during a colour change.
3- When you wrist feels tired or sore-- stop!!! Put an ice pack on around your wrist If you continue after this point-- you can do some serious damage!!
If you experience any pain/swelling in your wrist/or if the muscles on your forearm get tight and won't relax -- go see your doctor!! The sooner you do this-- the sooner you can recover an injury!!
I hope this helps a bit!! I just don't want people to experience the same thing as me!! Tendons can a long long time to heal if they are damaged.