I developed de Quervain's tenosynovitis (this is different from carpal tunnel syndrome) in my right wrist in 2007-2008. Weird, I thought, since I'm left-handed. The tunnel where tendons involved in moving the thumb was inflamed so much that I couldn't bend my wrist. The orthopedic told me to rest my hand regularly to minimise the pressure from moving it. I even wore a splint (supposedly for carpal tunnel syndrome, but I adapted it for my needs) to make sure my wrist wouldn't move too much. A few months on, I figured that the use of the computer mouse for extended hours probably caused the wrist to swell. It helped that I had spent a month separated from the computer mouse since I was using a trackpad in school.
I have learned my lesson. Too much of something is bad. An overworked hand will break down eventually. I should do everything I can to avoid a repeat of de Quervain's.
The typical computer mouse is set for right-handed users. So, to avoid overusing my right wrist (again!), I switch the mouse from right- to left-handed settings when the right wrist starts feeling painful. For fellow lab rats who plan to use the computer with the left-handed mouse, you have been warned.