Humans need something to struggle for constantly. Evolution wired us that way
Pretty good and succinct way to put things.
Look at different long term goals people have achieved and how it turned out in the end: Marriage, the storyline leading up to it is almost fantastical, about 50% of the time it ends in tears, even though the dream scenario plays out often... great relationship in the beginning, have the kids, buy the house... but after that the dragon disappears, the chase and the high are gone, then the realization kicks in that this isn't even what you really wanted, the fuck was the point.
I have a friend who's relatively young. Single, mid 20's, car paid off, money in the bank, about to finish college, ability to move anywhere in the country, and a couple of years into a career field where he's most likely going to hit the 6 figure salary threshold before he turns 35, maybe even 30, but every goal he achieves still leaves him feeling unfulfilled.
Or look at something simple like online shopping, how many times has someone revisited a page 20 times before they finally pulled the trigger and bought something they really wanted. It arrives and wow... cool... next.
Definitely an interesting subject to explore. Human's... funny thing that.