TODAY is Hiroshima Day, marking one of the most notorious dates in human history. On this day in 1945, 70,000 people in the Japanese city were killed by a single atomic bomb, with 10s of thousands dying of radiation sicknesses in the days, weeks, months and years that followed. It was the first of only two nuclear weapons ever used in human history, the other being three days later on the Japanese city of Nagasaki.

I have had the privilege of visiting Hiroshima, its Peace Memorial Park, and its Peace Memorial Museum. The one thing that struck me, aside from all the sites, photographs and emotions we’d all expect from such a tragic city, was how beautiful, spacious and peaceful it is for such a large city (its population is over one million).

If you go onto Google and search for Hiroshima under Images, almost all you get is endless black and white pictures of the nuclear explosion or the devastating effect it had on the city or the victims. However if you search for “Hiroshima now” you find an entirely different city. It has not only recovered, it has been reborn.

One of the things that mindfulness has helped me enormously with in my life is this understanding that things move on, but that often we do not move on with them. We get mentally stuck in images and views of past events, and this deeply affects how we see life. This can include how you perceive yourself, family members, your career, as well as political and social matters.

Consider just this short list plucked out of my head at random: not letting go of your partner’s past error of judgement, not letting go of your own mistakes or poor decisions, bigotry or prejudice or other forms of narrow disapproval, Margaret Thatcher, success or failure at school, arguments with your work colleagues or manager, traumatic events such as violence, major accidents, abuse, bullying, and the loss of someone we loved dearly.

Almost everyone carries at least one of these things around in their mind, related to events long since passed, or views formed decades ago. These weigh us down. We are so used to their presence, as part of who we are, that we usually don’t even notice them. But they colour our every moment, or to describe it more accurately, they dilute the colour in our every moment, making it greyer, darker. The potential joy in the moment is extinguished by what negative baggage we unwittingly carry around.

Two great Eastern teachers have commented on this natural tendency in people. The Vietnamese monk Thich Nhat Hanh teaches us to ask ourselves the question, “Am I sure?” when a negative thought, feeling or memory arises.

The Japanese Zen master Kosho Uchiyama put it more directly: “Open the hand of thought.” In other words, what pops into our head from time to time is so useless, so unhelpful, even so poisonous that the best thing we can do about it is just to let it fall into non-existence.

This is pure mindfulness. Awareness of what’s happening in the moment; noticing whether what’s happening is nurturing, neutral or negative; then deciding what to do depending on our assessment of what we notice.

The more we drop that which is unhelpful, the lighter we become mentally. We feel freed up, liberated, A sense of zest and fun returns. Life is seen as something to play in. The moment is, as my old Tibetan Buddhist teacher Tharchin put it, “a field of potential”.

To attain that mental state you need to dislodge and master all the junk and toxins that have become stuck in your head. This takes time, effort and regular practice of mindfulness. Whether it’s just noticing the way the clouds drift across the sky, rather than ruminating on an unpleasant meeting, or sitting formally noticing the way the breath enters and exits your body at the nostrils, it’s the same practice.

Lao Tzu, credited with writing the Chinese classic Tao te Ching, wrote that “the Sage is devoted to non-action”. Letting go is non-action. Try it. If Hiroshima can let go, without forgetting the lessons of its terrible day 72 years ago today, then surely we all can.