I almost always feel more tired after sleeping in.
For example, If I go to bed at 12:00am and wake up at 6:00am to an alarm, I feel somewhat tired, but after showering and eating breakfast, I usually do not feel tired at all.
If I go to bed at 12:00am and do not set an alarm, I usually wake up naturally, 8-9 hours later. I tend to feel much more tired when this happens, and for a much longer amount of time (usually until mid day/afternoon) even if I shower and eat right away like I would when waking up early.
I sometimes think that it is purely mental. Am I subconsciously forcing myself not to be tired on days that I must wake up early, but not when I am free to sleep in?
How is it possible that I consistently feel more rested after getting less sleep?