How do you deal with members here who are always depressed and bring your mood down?

If I think I can help, I offer an encouraging word. Some people don't want any help at all. I don't let their mood be mine and ruin my day.The only things I can't deal with are those I'm-here-to-spend-the-day-what-are-you-going-to-say folks. No matter what you say, they make a "fresh" remark or curse you out if you don't give them the last word. And you are just TRYING to be nice.