At first, when you push beyond your perceived capability your mind won’t shut the fuck up about it. It wants you to stop so it sends you into a spin cycle of panic and doubt, which only amplifies your self-torture. But when you persist past that to the point that pain fully saturates the mind, you become single-pointed. The external world zeroes out. Boundaries dissolve and you feel connected to yourself, and to all things, in the depth of your soul.