Steck Sie Rein!

It isn't true that your partner must be worn out in order to insert your fist. The human vagina is incredibly resilient, and muscle tone allows women to give birth, but also to tighten down enough to grasp a finger. Once she is comfortable with four fingers, you may press on till your palm is inside. If you are patient and take the time to let her build up, (usually after several orgasms) she may lose control and tell you just to fuck the shit out of her with your hand.