How about we continue with the subject of happiness? We already know that happiness is a state of mind. This state exists separately to the physical world and ultimately is a choice that you make on a moment to moment basis. If that is the case, then what are the choices one could make to produce this state as an ongoing experience?
The first thing to realise is, that regardless of how good the state feels, it cannot be continuous. Think of emotional states as drugs. This will help make sense of the whole subject. If you take a mood-altering drug for the first time it will have a profound effect. Keep taking the substance, and the body will produce a natural resistance to it. The mind and body adjust to the drug as being part of the current environment. In a sense, the drug has become the environment that it is operating within. The mind and body normalise the experience. As such, you no longer get the rush of sensation, needing more stimulant to reach the previous high.
Imagine this being the same concerning the subject of happiness. I call it emotional bracket creep. Like a taxation creep, you get a pay rise only to realise you have moved into a new tax bracket and discover you are now paying more in tax, placing you right back where you started. With one main issue, you are now just working harder to be exactly where you were.
Chasing happiness is like being on a hamster wheel. The faster you run, the more you end up staying exactly where you are. This is clearly expressed in the story of the phobic man. This man is terrified of footprints and mortified by his shadow. He decides one day to outrun both of them. As he begins to run, he produces more footprints and the shadow is right there with him. He decides to run even faster and then faster again, always producing the same result. He continues until he collapses and dies. If only he had just found a tree to sit under. There would be no more footprints and the shadow would have disappeared.
It is essential that there be ups and downs in life, this is the way we get to appreciate life itself.