How to lower cortisol without changing jobs.

Half past eleven. Last email sent, and you're in bed, shattered. Yet your mind is racing as if it were ten in the morning, and by 4am you're wide awake, going over tomorrow's meeting.

It's nearly always down to a hormone nobody has sent home: cortisol. Mind you, it isn't the enemy: you need it, badly. The trouble is when it's still on duty at eleven at night.

In the morning, you need it

After the overnight fast, cortisol raises your blood sugar and gets you going, peaking about half an hour after you wake. At night it needs to stay low: that shift belongs to deep sleep and growth hormone, which repairs your tissues.

Think of it as your best person in a crisis: you want them in the meeting, not in your bedroom at midnight, poring over files.

When it stops coming down

After months under pressure, this is common: your cortisol is normal in the morning, but barely drops during the day and is still up in the evening. You're tired but can't switch off, and you wake up flat just when you need a lift. So you have another coffee, soldier on, and by evening you're wired again. It's a vicious circle.

If this carries on, it takes its toll: your memory slips, your muscles respond less to training, your blood pressure goes up. If you've noticed these signs for weeks, mention them to your doctor too. It helps rule out other causes.

What keeps it switched on

• Working late. Emails at eleven, tense calls after dinner: late stress pushes cortisol up when it should be falling, and you wake up drained.
• The afternoon coffee. The 4pm one takes hours to clear. It's still in your system at lights out.
• Skipping lunch. When you run out of fuel, your body calls on cortisol to raise your blood sugar.
• Short nights. One five-hour night is enough: the next day your cortisol runs higher and you handle sugar less well.
• The drink to unwind. It seems to take the edge off, but evening alcohol breaks up your sleep: you sleep, but recover less.

What brings it down

The pressure of your job will still be there. How you time your day, though, is largely up to you.

Light, first thing. Same alarm seven days a week, then ten minutes outside. Easy here in Gran Canaria, I know, but it works in London in November too: even under a grey sky, there's more light outside than in the office. It's the signal that starts cortisol on time and, about sixteen hours later, brings on sleep.

Coffee at the right time. In the morning it works with cortisol, already high on its own. Last one straight after lunch. If even one makes you jittery, cut back in the morning too.

Your breath, on demand. It's the one stress lever you can pull any time, even in the lift. Five slow breaths, in through your nose for four seconds and out for six: the long out-breath puts the brakes on your nervous system.

Proper breaks. Every hour, two minutes on your feet. Take screen-free calls on the move, and after lunch, walk for ten minutes.

Train wisely. Few things clear stress like exercise. But if you're already under pressure, ninety gruelling minutes at nine at night add to the load, even if they feel like a release. Keep sessions under an hour, the hardest in daylight.

A proper wind-down. In the last hour, no emails, and soft, warm lighting. At dinner, don't cut out carbs completely: a moderate portion helps many people sleep better.

Your diary can stay as it is. Pick the easiest habit and keep it up for three weeks. Your body already knows how: it lowers cortisol every evening, if you let it. Your job is to stop fighting it.