You have a point, but your supporting assumptions don't make it. "In the long term things don't matter" doesn't matter unless you're going to be around in the long term to see them matter.
Either way, I wholeheartedly disagree with you. "Have fun, do what makes you happy" helps ensure that what you do doesn't even matter now -- never-mind it not mattering later. You are basically saying "since you can't be a god, you might as well not even try hard." It's black-and-white thinking at its worst.
You should do what you know matters; what your experiences are telling you is important. And even if 'you' die, the you that is a generic human with basic human needs and social identity will not die. It will live on in other people. You're not that different from humans that lived 50,000 years ago. The important parts of what you were then haven't died in that time. Make the world a better place for those who would live 50,000 years in the future -- because someone very much like you might want to know what you had to teach.
That person might even be an exact replica of you. Surely someone will generally want what you want and feel what you feel. Care for that person: they are your second chance.
I'm not sure you disagree with me as much as you think you do.
To clarify a bit more:
If being a successful entrepreneur is what makes you happy, do that. If raising a fantastic family makes you happy, do that. If tirelessly helping the poor makes you happy, do that. Yes, these things matter in the shortish term. And by "happy" I don't mean a minute-to-minute happiness. All of the things I do that make me happiest in the end are fraught with stress, pain and hard work.
My point wasn't that you should sit around watching reality tv all day, there are very few people I know for whom that would actually make them happy. It is just meant to put things into perspective relative to long-term thinking patterns like "how am I doing vis-à-vis the Joneses". It really doesn't matter.
I disagree that you should care about your own happiness. Happiness is not a meaningful goal unless you are willing wrap it in nonsensical notions like "actual happiness."
Actual happiness? How is that different from happiness?
My recommendation is to get good at _making decisions_. That way, should happiness be needed, you will be better able to produce it. But if you need something very different, you will be prepared to produce that, too. Happiness is just too myopic and selfish. Good decision-making will often result in happiness, but it's not the sole justification for it. (It will often result in unhappiness, too.)
Talking about long-term entropy isn't a reliable way to make decisions. If we think of 'meaning' as "that which separates signal from noise", you would be saying that -- eventually -- we will be unable to separate them. But we don't live in a reality in which that is the case: we can separate signal and noise right now. So arguing from that point is an argument from fiction. It's kind of like saying "we shouldn't build technology because someone might make the Terminator and everybody will die." Your responsibility is to make the Terminator first and design him so that he gives out hugs and candy. Or whatever else that is good.
I probably sound overly argumentative about this. You have a good point, I'm just trying to dig more deeply into it. I don't think there is a good answer to OP's concern. I would just say "don't worry, just consider your life an experiment," (as is my approach,) but then 'worry' is just part of the experiment. Maybe worrying about it is exactly what he should do. Maybe he shouldn't be happy. Maybe that's the only way to be a better person.
Either way, I wholeheartedly disagree with you. "Have fun, do what makes you happy" helps ensure that what you do doesn't even matter now -- never-mind it not mattering later. You are basically saying "since you can't be a god, you might as well not even try hard." It's black-and-white thinking at its worst.
You should do what you know matters; what your experiences are telling you is important. And even if 'you' die, the you that is a generic human with basic human needs and social identity will not die. It will live on in other people. You're not that different from humans that lived 50,000 years ago. The important parts of what you were then haven't died in that time. Make the world a better place for those who would live 50,000 years in the future -- because someone very much like you might want to know what you had to teach.
That person might even be an exact replica of you. Surely someone will generally want what you want and feel what you feel. Care for that person: they are your second chance.