Well recently some people I know have been going through some tough times and it makes me look back and wonder how I got through cancer (besides the meds....).
Fighting diseases, inner demons and such isn't a battle, it's a war (I hate to use those terms out of respect for those in the Armed Services, buts it's all I could come up with).
I think two things help. One is surround yourself with friends and family who offer a great support system and lean on them. Don't just hide away and cower! Use them (It took me awhile to ask for help).
Second, every morning get up and look at yourself in the mirror and say "Cancer (or what ever the demon is), I'm going to fight you all day today and do my best to win!"
At the end of the day, look back and yell at the nastiness again. You might not always come out on top, but try as hard as you can. "(Demon), you may have won the battle today, but I fought you hard and I'll fight even harder tomorrow! Too many people are counting on me. This war isn't over!" Every day do that. The mental aspect of winning far outweighs the physical.
I know it sounds corny and simple, but it's the attitude you have to take.
I hope this helps explain things and maybe help others out there who are struggling.