Happiness is often considered the goal of life, simply because it inherently feels good. To have a goal that doesn't feel good doesn't seem reasonable, yet happiness as a goal itself isn't rational for several reasons.
Firstly emotions are transient and ever changing.
Secondly emotions are typically beyond our control or beyond any control, certainly beyond our direct control. Perhaps any goal that is within our control is instantly undesirable, yet at the same time, a goal that is certainly beyond our control, such as a sunny day, also seems ridiculous. Perhaps it is because we feel we have some influence over our emotions, but not direct control, that we feel this is a good goal.
Thirdly happiness is a change in state, the inverse of sadness, rather than a state in itself. To be happy, you must simply change emotion from being unhappy. As the change is happiness, then it cannot be permanent as for every change up, we much also change down.
A more useful goal isn't happiness itself, but confidence that we can obtain it if we desire. Is this feasible?