What the depressed person needs most is understanding, patience and acceptance from those close to him. I have a self-help group that meets every week. If your spouse had a broken leg, you would expect that their abilities and energy would be restricted, that they would be in pain, and that they can't heal themselves more quickly just because you want them to. Think about depression the same way. Don't be provocative.
Every relationship has the little hot buttons that can start a fight at any time.
Dirty socks on the floor, the remote control misplaced, the car low on gas. You know what your partner's buttons are. Small acts of kindness are appreciated, and do help, even if the recipient doesn't reciprocate. When I retreat to bed, my wife makes a point of breaking in to kiss me good night. Even though I sometimes don't act very glad to see her, I would feel worse, lonely and unloved, without her attention.