Have you ever been surprised to realise how much someone else means to you – because they’re always there?

Have you ever realised you’d missed an interesting detail of your walk home – because you’d never looked up?

Have you ever found you’d forgotten to appreciate the small things in life – because you take them for granted?

The other day I was on a Skype call to a friend – her in the UK, me in Thailand – and she said something that gave me a jolt. In one of the pauses where I was checking something in my diary, my friend exclaimed “Wow, what beautiful birdsong!”

I was momentarily disconcerted – was she still talking to me?

And then I listened, really listened, and realized that the air around me was filled with a wonderful sound. Birds, all singing different songs, creating a harmonious and beautiful noise. When I first came to Thailand, I noticed it all the time, but over time, I’ve become accustomed to it and it’s faded into the background.

This phenomenon is called habituation by psychologists: when we are exposed to something over and over again, our original response decreases.

If our partner brings us a present for no reason, we’re pleased. If they bring us something every day, we start to take it for granted.

If we take a pill for pain, it makes us feel a little better. But the more we take, the more our body gets used to them so we need more to have an effect.

If we hear a loud noise, we’re startled. But if we hear one repeatedly – for example, at a fireworks display – we’re a lot less startled the thirtieth time we hear it than the first.

I used to live in a flat that was quite near a train track, where trains went past about six times an hour. When I moved in, the trains kept me awake, but after only a few days, I no longer noticed the trains at all.  Even guests who came for more than a few hours became habituated to the noise, not noticing it after they’d been in the house a short while.

Habituation is present in animals as well as humans, from the startle reflex in rats to a psychological study which found using an ‘unusual’ method of candidate attraction increased both the quality and the quantity of the candidate pool.

Habituation is an important evolutionary reflex, which enables us to function in everyday life.

It’s one of the ways in which we are able to focus our attention on the things that are important in our current environment. At any given moment, we are bombarded by bits of information hitting our brain in different ways. We can only pay attention to a small number of these at a time.

If we were constantly attending to everything that changed – a noise, a movement, a smell – we would quickly become overwhelmed by the huge numbers of stimuli in our environments and be unable to function.

But the flip side of habituation is that small things, beautiful things, can be lost to us.

Things that are a regular part of our environment can fade into the background – even amazing and wonderful thing, like birdsong.

One antidote to this for me has been travel, which, for example, has given me a new appreciation of aspects of my upbringing or country of birth – like education, the right to drive, and a free health service.

Travel, and seeing things in a different light, has changed my attitude to things I used to take for granted.

For example, living in Thailand, I buy drinking water, and no longer get this direct from the tap. It’s made me more conscious of how I use it, and reminded me that it’s a precious resource, and not something I simply take for granted.

One practice to stop taking things for granted is gratitude.

Taking a moment or two of your day to actively notice something you usually take for granted – the scent of your morning coffee, the hug your friend gives you to greet you, the laugh your partner gives at your jokes – will bring these small pleasures back to your attention, and mean that you feel happier without anything external needing to change.

But be specific.

Don’t just say you’re grateful for your mother, say you’re grateful to her for the way she’s always in your corner, or the awesome chocolate cake she bakes on your birthday.

I’m determined to keep being grateful, and watch out for habituation. I want to keep enjoying small background pleasures like butterflies, hammocks and birdsong, as well as the more obvious ones like new experiences, people, travel and the many other opportunities I am currently gifted with.

So ask yourself, what are you taking for granted? What have you become habituated to?

And how can you refocus your attention on the beauty, pleasures and delight which already exist in your own life?