So I'm totally new here, but found the subject of people with depression interesting.
I'm inclined to agree with MasterOfLightning on this because there are definitely two types of people when it comes to depression. There's a guy I used to be friends with who is essentially that person who does jack shit about his depression that he's had for years and blames everyone else as being the reason for it's existence. And to be frank, a lot of his "friends" have gotten fucking sick of his shit because he does absolutely NOTHING about it. He'll come up with an idea of how to get past it, but never follows through. Will see a therapist once, won't go again cause he thinks they're all whackjobs (not to say that some aren't). Will do all the drugs and drink all the boozes and will feel fine for a day and then go back to being hopeless. THAT is when someone who is depressed is being selfish. Especially if they only ever interact with people as a means to vent and be a whiny bitch. Not that venting is bad, it is helpful, but if you're constantly going to be an energy vampire, then piss the fuck off.
I'm going through a moderate depression rut myself after some major life changes and a part of it definitely is feeling lost, unmotivated, and like a sack of shit for a while. I'm at that point now and it sucks feeling unmotivated and lost (especially since I'm an A type deep down), but having gone through being moderately depressed before 1. Makes it seem less impossible, 2. Makes it easy to identity triggers and deal with them and catch myself when I'm falling into the toxic trains of thought/behaviors, and 3. Provides some motivation to not be unmotivated. Being an energy sucker to those around you isn't a good thing to be and it honestly makes me feel worse if I catch myself doing that. From the relationship POV though, it can def suck for the partner (believe me, I felt bad for mine when we were together, though to be fair they did lack some sense of empathy/understanding). But as mentioned before, if they aren't the only source of support then the depressed person is probably going about it the right way. A relationship isn't a fix all no matter how nice they may be.