Waves...no need to worry.
I believe I have seen situations of all kinds of levels of depression.
If it is severe, its best to talk with the doctor and work with him or her accordingly. And you make a good point about limitations.
Perhaps, as a person works there way out of the "darkness" they can implement this idea. And, for moderate-mild depression, this idea is a mainstay. Sometimes action can get a person out of depression (if possible and/or appropriate). Sometimes the action can be the least little thing...but just a small indication of moving forward provides a bright light of hope.