I've always felt these stories can be summarized as happiness or fulfillment is derived from the (positive) rate of change in circumstances rather than the achievements a person has in a point in time, money or otherwise. Even if you have millions in your pocket but that amount is not changing or you don't have a way to make it go up, you won't be happy for long. Same goes for a less wealthy person who is moving up in their career or their life-goals, they would be happy from experiencing positive change.