Your hand is a guide and a rest
A hand around the base does two useful things. It adds sensation for your partner, and it sets a natural limit on depth, so you stay in control. When your jaw gets tired, let the hand carry the rhythm for a while and use your lips lightly. Keep the pace steady and change it on purpose, not by accident. A little water-based lubricant keeps everything comfortable.
Pair it with Giving Head, the Complete Technique Course and read our oral sex tips.