A lot of people hurt themselves working out. They tweak a shoulder, blowout a knee, or they get tendonitis. Sometimes, it's a case of poor preparation. Sometimes, it's a few occurrence. There's a thousand ways you can hurt yourself while pushing your limits.
It's not ideal, and you shouldn't just accept it as a necessity, but you should know what to do when/if it happens to you.
And if you've already had a training injury, then, this you definitely need to read this now. If you've been lucky so far, consider it insurance.
Thanks for being part of the GMB Posse :)