"Every day you are either boosting or stealing your brain's reserve; you are either aging or rejuvenating your brain. When you truly understand this concept, you have a lot more influence in how fast your brain ages." Dr Daniel Amen, author of Change Your Brain, Change Your Life.

Have you ever noticed that two people can go through remarkably similar experiences, yet one seems to come through relatively unscathed while the other struggles for months?

Perhaps they've both retired after a demanding career. Or they're both caring for an ageing parent. Maybe they've both experienced a bereavement, a health scare or a particularly stressful period at work.

The circumstances are similar, but their ability to cope seems very different.

Why?

Part of the answer may lie in something called brain reserve.

It's a term that most people have never heard of, yet understanding it could completely change the way you think about healthy ageing.

What is brain reserve?

Imagine your brain has a reserve tank, rather like the fuel tank in your car.

When it's full, your brain has plenty of capacity to cope with life's inevitable challenges. It can adapt more easily, recover more quickly and continue to function well even when life becomes demanding.

But if that reserve gradually runs low, the same challenges begin to feel much harder.

Small setbacks seem bigger. You find it more difficult to concentrate. Your patience wears thin or you forget names more often.

The challenge itself may not have changed - but the amount of reserve available to deal with it has.

Why this matters so much in midlife

For many people, midlife is when the demands on the brain quietly increase.

You may still be working in a mentally demanding job while supporting older parents. You may be looking after grandchildren, adjusting to retirement, navigating hormonal changes or managing your own health concerns.

On top of that come the everyday pressures of modern life - constant notifications, endless decisions and rarely switching off completely.

It's hardly surprising that many people begin to notice brain fog, mental fatigue or occasional forgetfulness during this stage of life.

That doesn't necessarily mean something is seriously wrong. Sometimes it's simply a sign that your brain is working much harder than it used to.

The encouraging news is that brain reserve isn't something you're born with and then gradually lose. You can continue building it throughout your life.

In fact, midlife may be one of the most important times to start.

Keep moving

One of the most effective ways to build brain reserve is also one of the simplest: Move.

Regular physical activity increases blood flow to the brain, delivering the oxygen and nutrients that brain cells need to function well.

The good news is that you don't need to train for a marathon. A brisk walk, gardening, cycling, dancing in the kitchen or a short strength session all count.

Every time you move your body, you're investing in your brain reserve.

Embrace the new

For many of us in midlife, our routines are reassuringly familiar. We drive the same roads, cook the same meals and watch the same television programmes.

Your brain, however, thrives on novelty.

Learning something new encourages it to build fresh neural connections.

That might mean learning a language, trying watercolours, growing different vegetables, joining a choir, tackling a cryptic crossword or finally learning how to use that camera that's been sitting in the cupboard.

The activity itself matters less than your willingness to have a go at new things.

Novelty expands the brain.

Don't underestimate the power of friendship

One of the biggest surprises in brain health research is just how important social connection is.

Meaningful conversations challenge the brain in ways that puzzles simply can't.

They require us to listen, remember, interpret emotions, solve problems and respond in real time.

Whether it's meeting a friend for coffee, joining a walking group, volunteering or simply making more time for family, every genuine connection gives your brain another opportunity to stay engaged.

It's one more reason not to let yourself become isolated.

Give your brain permission to rest

This may be the strategy that surprises people most.

Many of us assume that building brain reserve means constantly doing more. In reality, your brain also needs time to recover.

Think about your mobile phone. You wouldn't expect it to keep working if you never charged it.

Yet many of us expect our brains to function brilliantly while running from one task to the next, checking emails late into the evening and squeezing every possible minute out of the day.

Rest isn't laziness. It's essential.

A good night's sleep allows the brain to consolidate memories and clear away waste products that build up during the day. Time in nature, moments spent in prayer or reflection, reading for pleasure or simply sitting in the garden all give your brain an opportunity to reset.

Sometimes the most productive thing you can do for your brain is to stop asking it to do quite so much.

Your choices today shape your brain

One of the things I find most encouraging about brain reserve is that it reminds us we have influence.

We can't control every challenge life will bring. None of us can prevent stressful seasons, unexpected illness or difficult circumstances.

But we can influence how well prepared our brain is to meet those challenges - by building our brain's reserve.

You don't need to change your entire lifestyle overnight.

Simply begin with one small step this week.

Because when it comes to protecting your brain, the best time to start building your reserve isn't someday. It's today.