I’m going to make a few controversial statements, but I believe they deserve to be heard and considered. I think that God, or nature – depending on whether you’re religious or atheist – wants people to behave in certain ways and avoid certain behaviors. For the things we are meant to do, there’s often pleasure involved. For example, God wants us to procreate, so he added pleasure to the act of sex. He wants us to eat to have energy, so he made food enjoyable through taste. On the other hand, there are things we’re not supposed to do, and pain is often associated with these. For instance, we’re not meant to marry close relatives, and this is evidenced by the genetic diseases that sometimes arise from such unions.
Then, there’s society. Society also has expectations for us – attend school, graduate from college, find a job, marry, buy a house, and so on. God, or nature, typically gets what they want from us by our twenties. Society, however, demands more, usually until our forties. After that, we’ve essentially fulfilled both sets of expectations. We’ve done what God or nature intended, and what society required of us. And once we hit a certain age, we find ourselves left to our own devices. Yes, there’s still residual work related to what God or society wanted from us, but, in general, we’re no longer needed in the same way. We’re left to ourselves. We’re alone.