I’m not sure where you’re going. Other things being equal, making the world better is a good thing and makes me happier. But there are many cases where the world getting better is in opposition to me being happy: if I donate $X to the most effective charity that does a lot of good, but also means I have $X left to spend on myself. The good done by the donation would make me happier, but spending it on myself would have substantially more of that effect.
I’m not sure where you’re going. Other things being equal, making the world better is a good thing and makes me happier. But there are many cases where the world getting better is in opposition to me being happy: if I donate $X to the most effective charity that does a lot of good, but also means I have $X left to spend on myself. The good done by the donation would make me happier, but spending it on myself would have substantially more of that effect.