We are our biggest enemy, when the mind is troubled it will bring down the body as well!
I myself struggle everyday with mental health and what seems to help me is mindfulness and peace of mind, I try to get rid of the negative emotions and replace them with positive ones, it's not easy!
Definitely not easy but once you're aware that you're the enemy the solution seems much closer than ever.
Another thing that seems to work and distract me from the negativity it's being busy, I need to keep myself busy doing something so I don't give time to my mind to start the negative talks, as soon as I'm idle my mind starts drifting to negativity lands and if I'm not quick enough to distract myself I can easily get lost and lose loads of precious time inside my self-imposed struggle...
Powerful thing the brain...