Tips for motivation and hope?

These past 6 months have pretty much been the biggest struggle of my life. I was diagnosed with a mental illness that incapacitates me in pretty much every way possible, and having to accept that and deal with it has been so hard.I go through periods of intense joy and productivity, and those are great, but then theres this horrible depression, and I can't move or think. I feel like I'm slowly ruining my life, and my will to live is dwindling. Please...if anyone has any advice for motivation and hope for the future, I can't say how that might help me.