This response isn't an exact quote but this is what he said.

People generally understand the concept of remission in serious diseases like Cancer and auto-immune. Diseases come and go. Depression is actually no different. It can come and go. It can go into remission. And then return. A person who is in remission for depression should not feel bad, or feel like they failed, because depression returns. A person who has cancer is not going think it is something they are doing wrong if the cancer returns after remission. Neither should people with depression.