Depression is a really terrible illness. Some people do not survive it. Many, many artists suffer from it. I've lost several artist friends to suicide, in that I worked in the arts for decades and knew many artists in lots of mediums. Perhaps that's why this incident hurts me a lot. It is a shattering loss.
Those trying to say, "Well, tough!" may not betaking Mick's broken heart into account. Rock star though he is, it will be difficult if not impossible for him to replace the depth of her whom he called his "best friend" any time soon, if ever in the rest of his lifetime. He is hurting. He is committed to performing again soon. It's a nightmare for him, too.
Depression is insidious, because it is often undetected. I think I have a mild version of it - the world often seems flat and lifeless. I can actually FEEL the depression, as a sensation. But I have a sense of humor, and I cope.
Having known “stars” over the years, I’m sure Mick is coping quite nicely. They are narcissists par excellence.
That said, he has written some amazing songs. I always advise people to ignore the artists and concentrate on their work.