If you wake up after 5 or 6 hours well-rested, that's all you needed.
If you feel like shit when you awake, and yet can't go back to sleep to catch up on the deficit, then you may have some variety of mood-affective disorder. The excess adrenaline makes and keeps you awake as soon as you rested a little bit in the first 5-6 hours. It also makes you dehydrated, and longer-term it forms a vicious cycle due to accumulated sleep deficit. This condition requires attention of a medical professional, which I am not.
If you feel like shit when you awake, and yet can't go back to sleep to catch up on the deficit, then you may have some variety of mood-affective disorder. The excess adrenaline makes and keeps you awake as soon as you rested a little bit in the first 5-6 hours. It also makes you dehydrated, and longer-term it forms a vicious cycle due to accumulated sleep deficit. This condition requires attention of a medical professional, which I am not.