Sometimes when I’m out walking and see a piece of litter on the ground, I pick it up and pop it in a trash can or into my pocket to throw out later. I don’t do this because I think anyone is watching, or because I’m upset that someone left it there. I do it because I believe the little actions that we take throughout our life can have big effects.

Economists use the phrase “marginal benefit” to describe the benefit obtained from performing an activity less the cost incurred. For example, a coffee shop owner would consider the marginal cost of hiring another worker for rush hour compared to the marginal benefit of selling more coffee and muffins during that period.

In bending down to pick up that piece of litter I’m not calculating the marginal benefit to the environment, I’m wondering whether when I stand up I might bump into my future wife or new best friend.

Only thinking about marginal costs and benefits is the right sort of behaviour if you’re a machine learning algorithm or a robot, but luckily human beings are able to think differently. We can realise that a series of little actions can add up to much more than the sum of their costs.

Picking up one piece of litter isn’t going to change the world, but it might be the serendipitous act that will change your life.

Everyone has the opportunity to make all sorts of tiny decisions during their day. Should I use my indicator while driving around that corner? Maybe I will say hello to that cute girl at the coffee shop on my way to work. Hey, that person has the same kind of camera as I do. They might like to talk about photography with me. Put in that extra rep at the gym instead of ending the set early.

There’s no doubt that my life would be completely different if it weren’t for a seemingly random set of small choices made over the years. I’ve been offered a job based on a five minute conversation many years ago at a conference. There have been more than a few engaging conversations had with strangers on the 14 hour flight from Australia to Los Angeles. I really did make a new friend simply by noticing we had the same type of camera.

So start living life at the margin, and don’t think that your small effort only has a small effect. The serendipity of everyday events can be the most amazing thing in the world.