We humans are social animals: we live in groups, form long-term bonds, and take care of each other.

Behind the scenes, we are also the caretakers of each other’s nervous systems. Here’s what I mean. Your brain works day and night to keep your body healthy by regulating its resources like water, oxygen, salt and glucose. This regulation is like a budget for your body. Actions that replenish your resources, such as eating and sleeping, are like deposits.

Actions that spend resources, like getting out of bed in the morning, your heart beating while you read quietly, or your immune system protecting you from viruses, are like withdrawals from your budget. Some withdrawals are even healthful, such as exercising and learning new things — they’re like investments that pay dividends later.

Anything that makes budgeting more efficient, like support from a loved one, is like a savings account. Anything that makes your budgeting less efficient, like being around someone who is unpredictable, who judges you, or is even harsh and insulting, is like paying a little tax. This is a simplified explanation, of course, but it captures the key idea that running a body is not a solo activity: body budgeting is influenced by other people.

Coordinated body-budgeting often has visible effects. Physiological changes in one person’s body often prompt similar changes in another person’s body, whether the two are romantically involved, just friends, parent and child, or strangers meeting for the first time.

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If you raise your voice, or even your eyebrow, you can affect what goes on inside other people’s brains, and therefore you can affect their heart rate or the chemicals carried in their bloodstream. For better or worse. If a friend is in pain, you can lessen their suffering merely by holding their hand. You can also heighten their suffering by ignoring or rejecting them.

Body budgeting can be particularly fraught during the holiday season. There are duelling holiday tropes: the warm and loving family gathering, and the nightmarish kind. If your holiday dinner is a cosy affair, you’ll reap body budget benefits. But if the main event at the dinner table is an inebriated Uncle Edgar and overbearing Cousin Kiki in a no-holds-barred taunt-slinging match, then it’s budgetary taxes all around.

So, here’s the takeaway as we move into the festive season: the best thing for your nervous system is another human. The worst thing for your nervous system is also another human. Close relationships are good for us. We tend to live longer if we have them, and get sick and die earlier if we are socially isolated or persistently feel lonely – possibly years earlier, based on the data. Without outside assistance to manage your body budget, you bear an extra burden.

With this in mind, it may be helpful to visit even very challenging people during the holidays for the benefit of your future self, so you don’t feel regret later. Regret is a painful emotion that can be a withdrawal from your body budget that may persist for years. And here’s a tip: if you make yourself predictable to other people, in all likelihood they will be more predictable to you, which translates into body-budget savings.

Also, when encountering friends, families and colleagues with whom you disagree, try to cultivate a spirit of curiosity rather than being confident that you’re right and they’re wrong. Who knows, you both might learn something. Granted, this is a workout for your brain, much like exercise is a workout for your body. So treat it accordingly.

If family gatherings aren’t for you, your body budget can connect with others in a variety of ways. Volunteer to help people in need. Be kind to a stranger. Run an errand for someone who could use a break. (When I’m feeling crappy, I bake bread or cakes for my neighbours.) The scientific evidence suggests that such moments of kindness may actually improve your own health and wellbeing, especially during times of stress.

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Lisa is a professor of psychology at Northeastern University and the author of Seven And A Half Lessons About The Brain (£14.99, Picador). She is one of the most cited scientists in the world for her research into psychology and neuroscience. Lisa is Chief Science Officer for the Center for Law, Brain & Behavior at Massachusetts General Hospital, and received a National Institutes of Health Director’s Pioneer Award for her revolutionary research on emotion in the brain.