One might look at life and see a sort of cycle where one fights one's way out of suffering and difficulty only to find a realm of boredom. That in this realm is not found contentment reflects an internal hunger that is never satisfied. People can be driven to pursue that which they can consume to satisfy that "hunger". Often this brings them back into the realm of difficulty and even suffering.
This cycle can be seen with someone who spends his Friday paycheck getting drunk and on Monday morning is broke again. There is another realm that one can enter but it requires one to set aside the selfishness that drives our pursuit of that which we can consume. As this perspective grows, boredom can be increasingly seen as contentment.
This realm is often entered by parenthood. The selfless giving of oneself to ones spouse and children can cause a deep soul satisfying happiness that is not often understood by those seeking after their own pleasures.
If one is dealing with brain chemistry compounds the difficulty in life finding happiness, a two pronged approach may be needed. Firstly, one might identify any actions that tend to bring one into despair and minimize them. Secondly, one can experiment with the various physical, nutritional, chemical, and situational influences on brain chemistry to learn what can be done to minimize the effects of depression.
One might see a goal of increasing contentment as a sort of "cake" while seeing happiness as "icing".