As soon as you are aware of depressing thoughts make a list of 15 things you can do to go into real depression. Then do the opposite. Here’s an example of a list I did a while ago:
Every little thing, that you do in opposition to your list will help you overcome depression. For instance refuse to yell at your son and wife, and refuse to watch TV. Clean the dishes, even if it’s only one plate. As soon and you’ve done one single thing you’ll get apetite for more
Now this will only help if your depression is due to depressing thoughts and not to a clinical condition. In that case you’ll have to take medication, especially third-generation antidepressants. But keep it to the selective serotonin reuptake inhibitors (SSRIs) (the other kinds are not well tried out). These have very little side effects and are not toxic.
But how do you know if you have a clinical condition? A good sign is that you have turned into a hypochondriac without a previous history of being one. Also your sexual appetite is less then it used to be. These are common signs, but of course a clinically depressed person will seldom admit these signs, but will persist that he has a one, or more often several physical illnesses. Especially if he is suspicious of physicians in common, he will not believe when they say that his bodily symptoms come from the depression, and that he needs to take antidepressants.