"Don’t cry, I know you’re trying your hardest," is a way to go when you’re dealing with somebody with depression. You don’t want to fall into the frenzy of "everything’s going to be okay"s and "you can tell me anything"s. Most likely, they’ve either heard it, heard too much of it or don’t want to hear any of it. But just to be as simple as letting them know that their efforts despite their imperfections are noticed: that’s more than enough.