basically, when our alarm wakes us up in the morning, instead of waking up naturally, we experience a surge of cortisol (adrenaline) in our body. the recurring using of an alarm, and accompanying adrenaline rushes every morning reduces the effectiveness for times when we would actually need it.
try waking up without an alarm on a day when you don't need to use one, see if it makes a difference in how you wake up, and your energy levels for the rest of the day.