Bottom drop, also known as sub drop, is the colloquial name for the intense feelings a bottom or sub may feel after a BDSM scene. These feelings often include depression or unhappiness, a jittery sensation, anger, or they may feel a bit "lost." The feelings experienced may vary depending on the scene, the sub's relationship with their dom/me, and the sub's values and beliefs.
Aftercare is very important after any BDSM scene to help manage the emotional after-effects.