Waking up on time is essential to good mental health. If necessary set your alarm, though if you can wake up without one, it's better still.
I generally set my alarm for six in the morning.
If you must go back to bed, don't turn off the alarm, but hit the snooze bar--if you honestly think you can spare another 5-10 minutes. It also helps to place the alarm a generous distance from your bed.
By rising at a set time every day--whether 5:30 or 8:00--you will get your body properly adjusted to its inner rhythms. This leads to better mood stability and decreases your risk for depression.
(Plus if you get up early, you can go walking or jogging before it gets too hot in the summer.)