[quote="Ja sa bong"]
You have to rest in order for your body to recover. It's like asking why someone sleeps at night. It's the same thing when you're playing too, you need to rest or you're going to hurt yourself.
[/quote]

Some injuries never heals 100%. So, it's best to make sure that whenever you're hurt, you do all your rehabilitation process very well to make sure that everything heals completely, otherwise you'd get a repeat of same injury again.