I have extreme fatigue a lot, and headaches sometimes. I also suffer epilepsy I guess people classify that as mental, but very rarely actually have a seizure however it causes me to suffer strong depression and fear anxiety episodes for couple of days every month. Also, it makes me very irritable and moody. Some people consider mental health to be a separate thing from physical but it isn't it affects your overall well being. I'm not crazy I just have a neuron misfiring going on in my brain.
To cope with my life (I used to be very sad that my life was so unfairly "ruined" this way, and I didn't deserve it) I now approach life differently. The main thing is to be grateful for every little thing in your life, to find happiness and contentment on the inside, to appreciate being alive! Study it, research it and adopt happiness as a way of being. It will change your whole outlook. Stop comparing your life to someone else's or to the way you think it "should" be and just appreciate it for the experience it is. Try using pinterest for quotes and things to help you learn about attitude and to get great advice in quotes. I wish you the best on your journey and I believe life is hard for every single person, it's just different challenges for different people, that's just how it is.