If you can guarantee that player is always unequal to NULL, you can omit the second check and just access you directly (given that both if() are related obviously). This would also work if you don't know wether player is NULL or not:

Code:
if(you && you == player)
{
   you->health -= 10;
}

Shitlord by trade and passion. Graphics programmer at Laminar Research.
I write blog posts at feresignum.com