The old man tells his grandson that in the soul of each person there are two wolves, between which there is a constant war.

One of them embodies fury, envy, arrogance, anger, fear and shame, and the second, tenderness, kindness, gratitude, hope, joy and love. The anxious boy asks: “Which of the two wolves is stronger, grandfather?” The old man replies: “The one you feed.”

I often remember this parable. It is a reminder that I decide which feelings I am growing and nurturing. One of them is gratitude or my ability to be thankful.

I realise that one of the most important conditions for happiness is to experience a sense of gratefulness for the people and things that I already have. I don’t want to think about what I would like to have, nor do I repeat with bitterness to myself: “Why don’t I have that? Why do I live differently than my friend? I would like another house or car.”

A feeling of thankfulness helps me to not envy other people, or to look for places where the grass is greener, and to think about what I do not have. I look thoughtfully at my life and find in it something that I can rejoice in and be thankful for right now.

Gratitude helps to focus my attention on the happy events of my life, the people who are meaningful to me, and the things that really matter. It encourages me to experience positive feelings more often.

Interestingly, studies in both Japan and America show that those who are accustomed to express gratitude in everyday life are more optimistic, possess a sense of harmony, and even feel physically better than others.

These people are happier because they react with positive thinking and are not inclined to condemn others.

Every evening, I close my eyes and I say one or two things I am grateful for. For example: “I am thankful for being alive and having a loving family.”

Often during the day, when I’m driving along a beautiful road and looking at the ocean, I say: “I am so grateful to enjoy this incredible beauty. Bermuda is so amazing!” These simple words warm my soul.

This is a very simple exercise but it helps reconcile a person with the inner and surrounding world. You and your family are alive and well, you live in an extraordinary place. Now, whatever is bothering you is seen from that perspective.

You can be thankful for anything: that you feel safe, that you are healthy, have a job, that your parents are still alive.

Or, you could be grateful for a lucky coincidence, for a sunny day, for a meeting with a kind person, even being thankful for other peoples’ success that you admire — we all have different lists.

Each person can find good in their lives. Everyone has their own reasons to be grateful. If we concentrate on them for a few moments, our negativity fades. If it seems to you that a particular day is the worst in your life, there is still some brightness in it.

When I am very upset, I clear my mind and look at the amazing natural world surrounding me. It could be an indigo sunset, the majesty of clouds, the roar of waves, the peep of tree frogs at dusk. Or, I notice the pure smile of a baby, the radiant faces of lovers, a firm handshake between friends. This distracts me from my unhappiness, and when I revisit it, I see it differently.

Gratitude is a choice you make. Like the wolf, you can sit on your own lonely summit, howling at the moon in self-pity. Or, you can race through the gleaming forest following the scent of happiness. The world remains beautiful. It is only how we see it that changes.

• Nina London is a certified wellness and weight-management coach. Her mission is to support and inspire mature women to make positive changes in their body and mind. Share your inspirational stories with her at ninalondon.com