I started weight training and yoga, and my wrist and back pain disappeared. I thought I was done and everything was fine.
But I was still sitting in a chair all day every day, and more than a decade like that herniated a disc in my neck. The initial symptoms were a persistent pain in my upper shoulder blade for months. The doctor said this would not have happened if I had just got up once an hour, and he sees tons of desk workers end up the same.
Since then I have seen some improvement by using a program to force me to look away from the screen at intervals, and to get up once an hour.
My posture is still horrible, but now the remaining struggle is simply staying aware enough to avoid bad habits (slouching, letting my head fall forward, etc).