Well, it's not because you had gotten more sleep. The longer you are asleep the deeper the sleep you go into, and when you get into a very deep sleep and you wake up, you get extremely tired and exhausted. I recommend less sleep if you want to feel better, I usually like around 4-5 hours asleep a day. When I wake up from like a 4 hour sleep, I actually feel revitalized and ready to do my day.
But, it also depends on how hard you worked your body that day. If you did some extreme working out and made your body feel exhausted, you will definitely be tired the next day because you're alarm will wake you up when you are in a deep sleep.
I think the worst thing ever though is waking up from a nightmare or dream and you aren't able to go back to sleep because you have work, school, etc. I say that because when you are dreaming you are in REM (Rapid Eye Movement) Sleep and this is the stage of sleep when you are dreaming. You only start to dream when you are in the deepest of a sleep and REM is happening. After all of the Dimethyltriptamine is released from your Pineal Gland into your brain, you will start to dream. If you wake up in this state of sleep, you are going to be VERY tired.