I'm not exactly sure what I'm going to say here. So this might be a little fragment of a start...
Depression is a disease that chokes you. I think of it like being in a pit, and I think of myself as a person who alternates among being in the actual pit, climbing out of the pit, lying panting on my stomach a few feet from the edge having just hoisted my way out of the pit, and walking along with roses and sunshine but always knowing the edge is right there and I need to give it wide berth so I don't slip in.
(I'm in the roses and sunshine phase right now.)
But I've been thinking about how depression affects our relationships lately, and have started thinking of depression as a snake that wends and winds its way around us and through us so that before a couple (a romantic couple, a parent and child, two friends) knows it, the depression is binding them and keeping them apart, and changing every interaction into something twisted and scaly, twisty and false. And then the snake starts swallowing whatever was in the relationship--the joy, the trust, the teamwork.
The only way out for the non-depressed person is to heave the snake off and leave, and then the snake is left with only the depressed person. Who is now alone in a pit with a hungry snake.
You can see how this is bad.
If you're in the middle of it, and you're the non-depressed person, you use your normal problem-solving methods to try to work things out and to compromise. But what you may not realize is that the person you love is being strangled by the snake, and you're actually trying to negotiate with the snake. No decisions you make, or make as a couple, are reasonable for the two of you as long as the snake is there, distorting everything and feeding on chaos and hurt.
If the only way to save yourself is to leave the relationship, then you have to leave the relationship.
But if there is any way for you to stay and wriggle out from under the snake and help the person you love to get away from the snake, too, that would be good. You can't save someone else, but you might be able to hold their hand while they're saving themself.
If I could have said it, back the zillions of times I was feeling it, this is what I would have said:
"I am still the same person inside. I just can't figure out how to connect that person on the inside to the outside. If you could push me in the right direction to help myself I will, but I can't see the horizon. Please don't give up on me."
You can't save someone else. But if you can see clearly and can figure out some first steps for the depressed person (who probably can't see the first steps for themself) that would be everything. And if the depressed person takes those steps, it would be amazing if you could hang out sometimes, and just hold their hand.
You can't save someone else. Sometimes people can save themselves if you show them the beginning of the path. Sometimes they can't. But sometimes they can.