Plato was a 4th century Athenian philosopher. I love this quote because it says that both being rich and poor makes not one happy. When you’re too rich you get lazy, and when you’re too poor you feel like crap all the time.
I think it accords really well with modern research that says being middle class, or essentially being in a position where money doesn’t affect you, is the ideal situation. You have enough to be comfortable, but not enough to be extravagant, and all your neighbours are in the same position. A $75, 000 annual salary should do the trick, says Time.