It's mostly psychological. You carry the emotion your dreams convey for some duration of time after waking, sometimes for the entire day. It depends on the magnitude of the emotion and how much attention you give it.

Having lucid dreams tends to leave me extremely excited and interested in my day, while having depressing dreams makes me pensive and slow to react, and dreams in which I'm doing something tiring make me want to lay around and rest for a couple of hours afterwards.

The fact that you're having the dreams means your body's getting the rest it needs. Just try not to let negative emotions interfere with your waking life; I have a feeling this is why people sometimes "wake up on the wrong side of the bed." (Regardless of whether or not they know they had a frustrating dream. )