how do you help someone who is dealing with depression

Depression is difficult to understand or explain. As someone who has been dealing with it for 35 years or so i can tell you that the strangest things will trigger it. When i am having a bad day and someone tries to make me feel better it usually has the opposite effect because i feel bad that i am making their life difficult. This is why many people who deal with depression become VERY good at hiding it from the world until it's too late. I will come on a website like this and discuss my feelings (about myself) but i won't do the same with family or friends in real life because i don't want them to feel bad but then i end up feeling isolated which is not good either....it is truly a vicious cycle.