This is a question I've been asking myself more frequently each day since the first time it occurred to me that I had power to decide whether or not to do something. As a child the choice usually boiled down to the old fun/trouble tradeoff and I would choose to do a thing if the fun experienced might outweigh the trouble I could get into for doing it. And even as a child that tradeoff bothered me because I was always wondering why stuff I shouldn't be doing had to be what seemed to hold most promise of so much fun. Part of it was born out of sheer rebellion. Rebellion to authority and conformity and normalcy, a natural tendency in most every human being. I enjoyed thwarting authoritative powers pressuring me to conform to behave at their perceived standards of normalcy. Screw that. I'm going to have some fun if it doesn't bring absolutely unbearable personal suffering in return. I tried to be careful not to do stuff which caused others any suffering, not always succeeding. That lack of success seemed to stem not so much out of personal malice as from inexperience and plain old stupidity–on my part as well as my cohorts' part in our endeavors to have fun which led to us into trouble.
Societal pressures mostly conveyed via programmed entertainment delivered via print, radio, TV and now the internet besiege us with an endless barrage of advertising attempting by any means possible within a delivery medium's constraining bounds to convince us we will never be happier than we should be if only we purchased products deemed by all makers to be the best of all ever made and which will ever be made forever and ever. But commercials lost their intended effect on me early in childhood after just a few attempts to find happiness in purchased products based on promises made by advertisements designed to sell them to schmucks like me.
Later in life, after thirteen years spent working as a common laborer while busting my feeble little brains to earn a college degree which would catapult me into professional careerism, I began to discover avenues of enjoyment gained by doing things both helpful, but more importantly, not harmful–to myself or to others. Increased income earnings professional jobs inevitably brought allowed pursuit of such benign pleasures because they could be afforded at last (as opposed to cheap thrills potentially harmful pleasure pursuits could bring without any upfront financial investment). So I pursued these new avenues of pleasure with gusto and more energy than I ever realized I had to expend on such things. Then it began to dawn on me that I could now choose jobs to lessen my negative impact on the world. So after spending the first half of my professional career years working in industries like advertising, petroleum exploration, private banking and enterprise web apps development for private companies and government agencies alike, I started my own company to help others seeking to do good things in the world without harming others at affordable rates. Twelve years of that career adventure was kicked off by making a documentary covering an obscure subject which most certainly would bring no monetary profit.
Why did I do that? Two reasons: 1) for fun, because I always wanted to make a film of some kind which delivered some degree of measurable positive impact, and 2) because it could cause no harm to others and might even bring joy and help some. So I spent the first two years and most of my startup money making the documentary. It was a lot of fun and I learned a lot about making film content. It wasn't anything earth shattering, but it did bring joy and it did indeed help others even though it never returned any profit and never even covered invested cost of making it. But I had spent my own money planning, shooting, editing and producing the final product delivered both on DVD and digitally (you can see the digitally-delivered product at Culture Unplugged and if you really want to obtain a DVD version there are a limited number of copies still around if you can figure out how to contact me to ask for and pay full cost for it (including shipping). But I'm not wanting to make money from it. I want it to convey to the world that enjoyable stuff can be experienced without harming others in any form or fashion.
After making the documentary I did some more enjoyable projects which caused no harm to myself or to others and twelve years working as a self-employed professional kept me fed and sheltered from hard times to the point they turned out to be my finest years of working life. Retired now, it's even easier to have fun without causing harm to myself and to others–a fortunate outcome of a lifetime of experiences so far. If I can maintain this do-no-harm course for another twenty or thirty years, give or take a few, then I'll meet my inevitable end feeling pretty good about it all and may even leave a wake of positive influence as I pass on.
A few memorable do no harm projects: