Happiness is a feeling of contentment, of feeling satisfied and fulfilled. While happiness is a pleasant feeling, it is often falsely equated with a state of inner peace. Placing “finding happiness” as your goal in life can perpetuate a cycle of suffering, as all feelings are temporary and come and go quickly. Many teachers from spiritual and psychological traditions reiterate that striving for happiness in itself will generally leave us feeling let down and unfulfilled, but striving for fulfilment and compassion toward others will often have the side effect of happiness.
Although she might never identify it as such, Byron Katie is espousing a form of meta-cognition, a way of thinking about thinking. Are your thoughts a true reflection of the reality around you, or do they come unbidden from your unconscious?
Stoicism holds that the key to a good, happy life is the cultivation of an excellent mental state, which the Stoics identified with virtue and being rational. The ideal life is one that is in harmony with Nature, of which we are all part, and an attitude of calm indifference towards external events.