More money leads in almost all people to artificial value, short term superficial happiness, degradation of the soul. On the outside it looks great and shiny, but on the inside the soul starves and craves true happiness. Unfortunately, most rich people react unconsciously by spending more and more, in a desperate effort to fill the ever growing gap.
Longer term less money creates in almost all people higher valuation of the most simple and basic things, which translates to true happiness for the soul. Less money can restore happiness if people are willing.
But there is of course a lot more affected by the money in our lives, especially the ego. A rich men easily thinks he is really someone, a 'great' man, special, gifted, etc.. The poor man will most often struggle with the opposite thoughts and feelings, while in the end it's all false.
If I ever again have quite some money to spend, I'll be very vigilant, you'll see me desperately trying to hold myself back. Never trade your soul for money (or power) is my advice. And if you have a lot of it, use a substantial part to help poor children for example, give them food, education, that will create you some ever lasting happiness, at least, if you can hold yourself back from growing your ego on that.