It is your reward. The sensory organs in your body are congratulating you for a job well done, whether the deed achieved conception or not. In the final moments before the deluge, your body is optimized to “put out”. Very little will stop you from achieving that goal if you intent is to proceed until fruition. For me, when younger, it was almost as if a demon had taken possession of my physical being and the end benefit was ejaculation. There are not a lot of feelings that are as intense