whenever you hear the term depression, pull back and think to yourself things you've said to other people in regards to depression. Personally, its rare that I do, because despite things getting to a point where others would normally succumb to depression, I try to be realistic as possible but also find ways to be and remain positive as to not let depression become a hindrance rather than be hypocritical and tell people not to worry so much if that be the case for me one day and thats the only thing I am thinking about/worrying about.
Usually just have that kind of attitude about everything to help, even nearing depression. Or when I actually am depressed, several things can help such as talking to another sympathetic yet rational human being. Friend, or otherwise professional.