It's different for everyone, but one thing I've found that's been tremendously helpful for me (in 30+ years of programming and heavy W-A-S-D gaming) has been th

It's different for everyone, but one thing I've found that's been tremendously helpful for me (in 30+ years of programming and heavy W-A-S-D gaming) has been the use of ergonomic devices (keyboards, mice) and workspaces (desk height, position, chair, posture, etc.). In particular, ergo keyboards allow me to type comfortably for hours on end, day after day, year after year, at very fast speeds and without any injuries so far. Before I switched, I would get all sorts of finger and hand cramps monthly. I personally like the Microsoft Sculpt Business keyboard the most, but that's currently discontinued (soon to be re-released under the Incase brand). There are many other brands & models, both with soft laptop-style keys and harder mechanical keys. I particularly like the Microsoft one because it doesn't have an attached numpad, which means your mousing hand can fit comfortably next to the keyboard instead of stretched out unnaturally far away. (The numpad is wireless and can be placed anywhere, for the rare times you need it). There are also many types of mice, from wrist mice to vertical mice to trackballs to simply flat mice (like Magic Mouse). I found alternating between the Magic Mouse and a trackpad to help with mousing pain. You can also use webcam-based eye tracking if you prefer, or like foot pedals for scrolling.