Hi M.,
I see two questions in your request for advice. One is, how do you help people get unstuck when they are sad and in a rut. Two is, how do you bear it when your friends are repetitive and tedious, and the stories they tell are always the same? I'm going to sort of ignore question two, because I get impatient the same way you do. Hopefully Megan has an answer. I'll talk about question one.
I think it's possible to get unstuck when you're sad and in a rut. I spent the last four years as a coach -- first in a physical, athletic, realm, and now in the realm of helping people choose and find work that suits them. I believe in goals and accountability, and social support as ways of getting out of a rut. I have some specific ideas that have worked for me and for people I know.
I also think that people choose their own coaches, so you can't choose to play that role for your friends if they haven't chosen to be accountable to you, to invite you into the process of helping them set their goals, etc. If you take on that role without your friends' participation, you'll be frustrated and ineffective and they will probably resent you. What people want from coaches is a kick in the butt and clear, measurable goals and motivation to get to it, and a little bit of a fear of losing the coach's respect if they do not perform -- accountability. What people want from friends is unconditional acceptance, sympathy, understanding, humor, comfort, and a reminder of their best selves. I do think as a friend you can reflect some of that back: you can remind them of what you love about them and who they seem to be to you, you can say, I hate seeing you blue like this, because I know a different you and I can't wait until those happier sides of you have full expression again, you can ask questions about why they're acting in a way that you don't fully understand, you can ask, "what do you think you should do?" and follow up with, "how did that thing work out for you?"
As far as sadness goes, I have great respect for depression: it's a disease, and it gets worse with time, and it can be treated and should be. It's also a habit of thinking, so in addition to chemicals it can be tackled with a change in approach, through cognitive therapy. You are right to be distrustful of the constant repetition of sad sack stories -- I'm not sure there's any value in catharsis or expression of sadness, and there's a pretty strong risk of reinforcing a mental pattern of helplessness, worthlessness, and unlovability. That thought pattern goes away with treatment, but it gets more powerful with repetition and reinforcement, so there's not much value in indulging it. I think your role as a friend is to redirect, to fight the bad habits of mind that are likely to strengthen depression's hold. Even some other things: going for a walk with your friends, asking them for help with a project, will reframe the friendship, and will remind them of what they can and do contribute to your life. Some activities absorb our attention and leave us feeling better than we did before we started them -- making things, doing absorbing and hard physical activities, learning a new skill. As a friend, you can perhaps invite these friends to participate in concrete activities that remind them of what they can do rather than what they can't.
There's a longer conversation to be had about whether depressives see reality more clearly or have greater insight into depth and human pain; or conversely whether to be cheerful and content means you are necessarily more shallow or more deluded. There's some evidence for each view, and I am not completely sure where I land on that conversation. I'll admit to being uneasy and suspicious, at times, of my own cheerfulness and unearned high self-esteem. (This issue is well-addressed in Kramer's Against Depression.) But when it comes to the people I love, I like to see movement and progress, a feeling of empowerment and growth, a sense of confidence. And in the case of chronic depression, that's something that professional treatment can help with.