Well, I recently had the stomach flu. With a low grade fever and generally feeling rather miserable, though in a different way than mental illness. Thankfully, it didn't last long. But it reminded me of depression in how I just felt very yucky in a very concentrated way.
So anyway, from that experience came my advice for people wanting to give spiritual advice to people struggling hard with depression and/or anxiety. Here it is, straight from where I shared it on Facebook (not so sure how good an idea it was to put it on Facebook, but maybe I'll find out):