Remember, dying is never a good way to end a workout....
~Peter Fortuna 1999
Sometimes beginners or advanced individuals will work to a point well beyond their safety zone. It's important to remember when this happens bad things usually follow. Think sprains, tears and even death. There's a fine balance between working out and working out crazy.
While we all should work as hard as we can- safely; it's never a good idea to push your body past its limits and into ahem... an early grave.