I once had a therapist who laughed – not just a chuckle but an unrestrained, full-bodied laughter. Initially, it took me by surprise. I thought therapy was a solemn endeavour, a place to unearth my deepest fears and sorrows. On a significant birthday she asked to see photos of my party, her eyes sparkling with excitement. She joked that we could have had a bottle of champagne in our session to celebrate (we didn’t but I appreciated the sentiment). She never missed an opportunity for shared joy.

Of course, we also did the hard work. She witnessed tears, frustration and confusion – often before 9.45am. She had seen a lot and had sat through a lot. She had been a tireless advocate, frustrated with a system that abandoned many of its vulnerable in the name of efficiency.

Years later, as I prepared to lead a presentation on what Buddhists call mudita – often translated as appreciative joy, or rejoicing in the happiness of yourself and others – her laughter came back to me. On the morning of the talk I went for a walk and vowed to notice joy in the world around me. I stopped and watched brown ducks shaking their feathers by the lake. I watched children climbing precarious-looking play equipment and received an unprompted smile from a stranger.

These weren’t remarkable moments. And yet the more I lingered, replaying them in my mind’s eye, the more I couldn’t stop smiling.

Appreciative joy, sometimes also referred to as sympathetic joy, is one of the four qualities the Buddha encouraged practitioners to cultivate, alongside loving kindness, compassion and equanimity. It is often described as a state of mind that rejoices at the wholesome happiness of the self and others, and extends to all beings, including strangers and (as hard as this might be) our enemies.

It is not superficial excitement or uncritical Pollyanna positivity, nor is it pleasure that arises from engaging in or witnessing self-centred gratification or unethical gains. It is a joy that is grounded, steady and sometimes subtle. Contrast it with envy; a widespread social emotion that damages society’s psychological health and wellbeing.

Yet appreciative joy is often overlooked in modern Buddhism, which has tended to focus more on compassion and love (also important, of course). It is under-researched in psychology, where empathy is studied mainly in relation to suffering. Most social institutions emphasise empathic sorrow, not empathic joy or what is now referred to as “positive empathy”. We are encouraged to care for others’ pain but not to celebrate their success and happiness.

Appreciative joy is low-hanging fruit: it’s free, simple and immediate.

Research also suggests that training in positive empathy can reduce social media-induced envy and lead to greater life satisfaction.

This is echoed not only in psychology, but also in spiritual traditions. The Dalai Lama once said that when we rejoice in others’ happiness and success, we multiply our chances by billions. These are good odds!

And yet the spirit of appreciative joy runs counter to many of our habitual ways of relating to the world. As the sociologist Pierre Bourdieu observed, in a stratified society we are often conditioned to see another’s success as a threat to our own status. Social media can intensify this, fuelling “upward social comparisons” which are linked to increased anxiety, depression and Fomo.

Of course, appreciative joy on its own will not fix structural or global injustices, nor will it solve complex social issues. But it can provide those of us caring for others and advocating for change with nourishment and connection, which can sometimes feel out of reach.

It moves us beyond a narrow self-care framework into mutual celebration and solidarity. It is one way we can apply Buddhist ideas in contemporary times that can guard against burnout and sustain the work of care and courageous advocacy. As the social commentator Rebecca Solnit writes: “Joy doesn’t betray but sustains activism. And when you face a politics that aspires to make you fearful, alienated, and isolated, joy is a fine act of insurrection.”

And here’s the secret: you don’t have to be happy to practise appreciative joy. You can unapologetically draw on others’ successes to gladden your heart. As a pessimist, I would have once rolled my eyes at this idea but I can’t deny that it helps you sit with difficulty, yours and others – and it shifts you out of negative, ineffective mental states that cause unnecessary harm to the world around you.

The evening after my talk, I had a realisation. Even if my lecture didn’t land as I’d hoped, I could still drop my fretting and focus on my students’ accomplishments: their wisdom, their moments of peace and their hard-earned successes. I didn’t have to be the centre of my own happiness. And I laughed, the raucous laugh of my dear therapist, who knew that joy isn’t optional – it’s a necessity.

• Dr Nadine Levy is a senior lecturer at the Nan Tien Institute. She coordinates its health and social wellbeing program and the graduate certificate in applied mindfulness