As the other replies have said, if you are good at being in the guard then you should be fine. If you grapple often then you won't have too much trouble there. The problem can come if you are uncomfortable there and start to panic. If it is a vicious fight and you find yourself in the closed guard, pullhim in and simply eye gouge him. Fight is done. If you don't want to eye gouge him, set him up for something less brutal, I.E. a choke out.