You might think of yoga as gentle and restorative (at least, until you know better, and realize that yoga can kick your ass) but that line of thinking can be dangerous. ANY activity comes with inherent risks, and yoga is no exception.
You can get hurt. Really hurt. A recent New York Times article outlines just some of the havoc that yoga can wreak on your body.
Luckily, I can't speak from too much experience here. I have yet to injure myself in yoga (knock on wood). I think I have, however, come close. One time, I was so deep in a twist that I felt this weird, sudden shift in my ribs-- it didn't hurt, but it startled me, and I came out of the pose right away and everything was fine. Another time, as I was working on a bind, I felt these weird shocks all of a sudden, like mini bursts of electricity shooting through me. I assumed I somehow touched on a nerve, and again, it didn't hurt, but I came out of the pose thinking, "Whoa." I probably shouldn't have done that. I probably take my backbends too far sometimes, and wake up the next morning more tender than I should be.
It's a fine line to walk: on the one hand, you want to push yourself, and you're doing all this funky stuff with your body that you've never done before, everything's so unfamiliar! How can you tell when you cross the line from challenging and new to dangerous and over the edge?
For now, my answer is: know thyself. I know I have a tendency to push it, so I need to work on playing it safe. Not wussing out by any means, but respecting and protecting my body. It's just not worth an injury that will leave me out of commission for weeks and weeks!
So now, readers out there, what do you think? Have you ever injured yourself in your practice? Have you come close? How can you tell when you're flirting with danger?