I had someone tell me that someone who is seeking happiness through external pursuits, when they attain what they are looking for, will find it lacking and look for the next external pursuit, thinking it will fulfill them, only to find it is lacking also. For example, someone who thinks that the next big car will bring them happiness, when they get the car, will drive it for a while, then are bored and want the next car or a house or promotion, or whatever. They go from pursuit to pursuit, always looking for happiness, only to be disappointed. Happiness needs to be an internal pursuit, not external.
I cannot add anything to this article. It speaks to me: