My timid mother was the ultimate people pleaser - until the day she stared down racist bullies... and taught me to channel the power of defiance. Here's how you can too

As a child, my mother seemed the embodiment of compliance; unaggressive and unassertive, she always quietly deferred to others. A small woman in a sari, she epitomised selflessness, smiling pleasantly in response to every request, be it making fresh rotis for my dad or looking after a neighbour's toddler. She never said 'no', even if she didn't have the time or the energy. Yet, when I was seven, Mum shocked me with a brave act of defiance, showing a side of herself I hadn't known existed. Walking home together from the supermarket, our rickety shopping cart loaded with groceries, a group of five or six teenage boys confronted us down an alleyway.

My parents are first-generation immigrants who had moved to Bradford from India. 'Go back home,' one of the boys yelled at us, as the others laughed. A couple tried to block our path. My instincts told me to say nothing, avoid eye contact, avoid confrontation. I grabbed my mother's arm and tried to manoeuvre quickly past the boys. But that day my quiet, compliant mother shrugged me off and, with a firmness that shocked me, pulled the shopping cart vertically upright.

Her face was set in a determined scowl, her hand on her hip. She is 4ft 10in at most, but suddenly she looked taller. 'What do you mean?' she asked in a clear, uncharacteristically strong voice. As she stared the boys down, they suddenly seemed cowed, their eyes darting to each other. None of them answered. 'You think you're so strong,' my mum continued. 'Big tough boys, right?'. UK professor Dr Sunita Sah (pictured right, next to her mother) shared her advice for practicing defiance.

One of the boys muttered 'let's go' and they dispersed. After they'd gone, Mum carried on walking, head held high, her green sari trailing behind her in the breeze. I realised this must have happened before. The times she had come into the house muttering angrily to herself, she must have encountered these boys – or people like them – for years. But that day, something changed. She was tired of giving in. Finally, she said 'no' – no to staying quiet, no to putting up with bad behaviour. It was a firm declaration of her boundaries and values in a way I hadn't seen before.

Years later, I reflected on this when I began researching the dynamics of compliance, during an extra year studying psychology I opted for during medical school. As women, we are raised to be compliant, learning as children to equate saying 'yes' and pleasing others with being 'good'. But that conditioning makes it harder in adulthood to call out bad behaviour and to say no, even when something feels wrong.

Dr Sah shared about an instance where she had seen her mother, pictured, stand up to racist bullies. My studies made me consider all the times I had tried to say no to an unfair request from a teacher or to resist expectations from family or friends, yet smiled and complied, just like my mum so often had. I've stayed silent in meetings as someone has taken credit for my ideas and done the same in group discussions when people presented as fact things I knew to be wrong. On one occasion, I even agreed to a CT scan my medical training told me I didn't need because I didn't feel able to question my own doctor.

That incident in the alleyway showed me defiance sometimes comes from the people you least expect. And although it often looks like an instantaneous reaction, its progression – from feeling, to intention, to action – can take a long time. That day my mother gave me a lesson in what it means to defy – and that defiance isn't about personality. It's a skill, a deliberate and thoughtful choice. And one that can be learnt.

Today, I am a physician turned organisational psychologist and Cornell University professor. In my new book, Defy: The Power Of No In A World That Demands Yes, I present my case for defiance being the courage to act in alignment with your values, even when societal pressures push you to comply. Defiance requires training yourself to act differently, because your brain has been hard-wired since childhood to associate defiance with being bad. Breaking this good-bad binary allows us to access our truest self – and feel happier and more confident for it.

Here are some tips to help you do just that... KNOW YOUR TRUE YES. For 'no' to really mean no, we need to know when 'yes' means yes. A friend of mine has a saying: 'Don't say yes unless it's a 'hell yes'.'. It's based on how genuine consent often feels good. Compromising on your values – acting to please others at a cost to yourself or someone else – doesn't feel good and often creates tension in the body.

That can be a feeling of powerlessness or physical sensations such as unease in your stomach, tension in your neck or a headache. Next time you're asked to do or go along with something that doesn't sit well with you, acknowledge that discomfort – it's your internal compass, guiding you back to your values, urging you to say 'no'. A true 'yes' will feel comfortable. Dr Sah, pictured with her other, revealed how you too can channel defiance by practicing it and 'breaking free' from politeness.