This post is really problematic and has incredibly dangerous applications of the philosophy spilled — let me explain.
Encouraging people to be ‘useful’ is a very utilitarian philosophy, encouraging a sort of ‘net good’ being given out of someone’s life in order for it to have a sort of purpose. It’s not an uncommon view, it’s been detailed in philosophy for centuries, but it’s incredibly troubling for a multitude of reasons.
First, it implies that people who don’t live a ‘useful’ life have essentially no purpose, have done nothing with themselves and been a useless addition to the world. I don’t know about you, but save for the absolute most heinous of people in history, I wouldn’t describe anyone in a light that implied their life has a sort of value. Everyone’s life is worth something, it has an intrinsic value to it — it’s something that should be recognized and appreciated, not be given a moral price tag. I don’t believe you, the author of this, feel otherwise — most people don’t, but it’s an undoubted result of this sort of philosophy.
Secondly, it ignores those who physically *cant* be ‘useful,’ such as say those trapped in poverty, those dealing with debilitating disabilities or mental illness that prevents them from making any sort of ‘useful’ impact. It needn’t be said that millions in poverty, with disabilities, with mental illness make amazing impacts to the world and to history — no one argues otherwise — but of course many lack the resources to do anything but to barely make ends meet, to be able to get through the day, and so essentially it implies that they have no ‘use’ and live a worthless life. Again, I don’t at all take you for having this position, but it’s something that falls from what you argue.
Thirdly, and this one is incredibly important I feel, encouraging ‘usefulness’ as opposed to ‘happiness’ is really troubling considering it’ll only lead people to do things they believe are morally good at the cost of their own well-being. That’s not a life that ought to be encouraged — it’s built around constructs of virtue that only end up bringing someone down instead of up. Since you do things that are ‘useful’ because you want to leave a positive impact and want to better the world, I’m sure you agree that people living their lives contrary to how they’d like (provided that how they like doesn’t harm others) isn’t exactly a solid ideal.
None of this is to say that encouraging action, encouraging people to make a difference is bad; it isn’t at all. I try to promote the same thing and to live by it myself, but it isn’t contrary to an overall pursuit of happiness; if anything it’s completely in line with it. We all want to make the world a better place, so why don’t we make it a happier one for everyone?