Life can certainly make you tired, especially if it's a stressful life. Simply thinking about things in my life can exhaust me.
I would answer the questions that CyclingFitness has listed for yourself. Exercise might also help--and that doesn't have to be an added stressor. Simply getting out of a chair and walking around a room can reinvigorate a person.
I hate to say this, but it's on TV commercials all the time: depression can make you tired. If you continue to feel this way, no matter what you think it might be, you should see your doctor to rule out anything else.
Best wishes. :)