I have quite a lot of energy, but I know some people just aren't as lucky. Is their a medical condition for being constantly tired?
I think it's called Chronic Fatigue Syndrom, or CFS.  I don't know a lot about it, but it makes people tired for long-term amounts of time.
That must be awful. I wonder what causes it. Depression perhaps?
I don't think the cause is fully understood.  It could be genetic, could be biological, or it could be psychological.