What is happiness
I think a big part of attaining happiness in our lives is to first understand what happiness really is. I find it is a very misunderstood concept, most people mistake joy or ecstasy for happiness.
I think of happiness like this. I'll use the analogy of a ship, or a boat on the water. Water can be choppy, with high or violent waves, or calm and settled, much like life. When the boat rises up on a wave, this is joy. When the boat goes down lower than the water level, this is sadness or despair.
What matters, then, is the depth of the water itself. In the middle of an ocean, going up or down a little won't impact the ship very much, but in shallow waters, going down below the water level may cause the boat to smash into rocks or reefs, rendering sometimes catastrophic damage.
Happiness, then, is the depth of the water itself. If you live your life in a state in which you have a great depth of happiness, then the lows won't bother you very much. The highs are still highs as you ride the crest of the wave.