Ignoring our anger can make us believe that nobody counts and nothing matters. Professionals debate whether major depression is biological, psychological, or both. But everyone agrees that all depression, mild to severe, shows the need for better self-care. To the extent that this is true, it is a sad reflection of our guilt-ridden culture. It is not a reflection of some biological predisposition toward being depressed.
Any depression is a problem, and regularly occurring depression is a serious problem.
If you are seldom depressed, read this section for general ideas on self-improvement. If you are often depressed, work your way down the list and spend as much time on each item as you need. Just go about your normal day and notice every time you see even the slightest sign of anger in the people around you. Decide to learn from those who do not. Put an asterisk on the examples you like most.