When you have me not, you want me. But when you have me, you do not know. What am I?

Why this works

This riddle plays on the contrasting states of desire and awareness regarding sleep. When you’re awake and restless, the longing for sleep is strong—you crave the rest and rejuvenation it provides. However, once you actually fall asleep, you lose consciousness and awareness, making you "not know" that you are sleeping. This clever juxtaposition highlights how we often yearn for something that we don't appreciate fully when we have it!