In sports and other physical activities there's a lot of focus on proper form. The reason for this focus is the simple fact that the human body is built to work in certain ways, and if you insist on doing something--especially at a high performance level--incorrectly for how the body is put together, you're going to hurt yourself.

While sitting at a desk and typing won't be confused with a high-performance sport any time soon, this activity also has the chance to severely mess up your body if you're not careful. For my 30th birthday (mumble) years ago I got my body a good computer desk chair as a thank you for getting me that far, and in hope that it would get me farther still. I also educated myself about ergonomics, which is for our purposes the science of arranging our work areas so that it best suits our bodies.

I cannot recommend enough that you take the time to ensure that your workspace is ergonomically arranged. You will save yourself having to hear diagnoses such as carpal tunnel syndrome and other such unpleasantries. Though keep in mind that of course no two bodies are alike. Some people swear by switching from a mouse to a trackball. Others prefer speech to text software so they can keep their typing to a minimum. Personally, I have repetitive strain issues that make it smarter to mouse with my left hand rather than with my right, even though I'm right-handed (and I use the mouse still configured for the right hand, rather than the left). 

Wondering what this has to do with freelance survival? Well, for one thing you can't work if you cripple yourself. I could barely type for a month with my right hand, which put a severe crimp in my projects. And for another, hopefully your aim is to not just survive, but to do so while being healthy and happy.