Unresolved emotional issues can cause physical exhaustion. THe body and mind are absolutely connected.
When I was able to quit drinking, quit using drugs and finally quit sugar, my energy levels increased. I went from being a couch potato to a daily runner. I followed a low carb, low sugar, high protein diet. I cut back coffee to one cup a day and made sure I got enough sleep.
Addiction is exhausting. Lack of emotional sobriety is also exhausting, even if you're not actively using. In early recovery I slept around the clock some weekends, other times I couldn't sleep at all. Therapy and abstinence over time has given me a lot of energy back. I'm 40 and feel better than at any other time in my life. Quitting sugar was the final key for me. It's as much a drug as alcohol or heroin. My mind is clearer and my thinking sharper, too.
I have a number of other health related issues, including long standing untreated chronic fatigue. A good naturopath has helped enormously too.