Jules Benjamin, a close friend of my father, used to say, "Money doesn't buy you happiness, but I don't mind being miserable in comfort."

We live in interesting times. On the one hand, never in the history of the human race have our lives been physically easier and more comfortable, and on the other, never has emotional dysfunction been so prevalent.

In other words, never have we been so comfortable - and been so miserable about it.

The United States of America, the world benchmark of affluence, has 18.8 million citizens affected by depressive disorders; that's 5.4 per cent of the total population. Four per cent of pre-schoolers are clinically depressed and the rate of increase of depression among children is 23 per cent. The percentage of the population in developed countries that suffers severe depression is 15 per cent. Thirty per cent of women are depressed, and 41 per cent of them are too embarrassed to seek help. And just to cheer you up even further, the World Health Organisation reports that every 40 seconds someone takes their own life.

Of all the Jewish festivals, Succot is most connected to simchah, to happiness. In fact, Succot is z'man simchatenu, not just a happy time, but "the time of our happiness".

The idea of setting up home in a draughty booth doesn't conjure up thoughts of simchah

What's so happy about Succot?

Ironically, Succot, especially in England's green and pleasant land, can be distinctly physically unpleasant. As a child, I well remember being shlepped by my father through the succah of Hampstead Garden Suburb Synagogue after davening. The floor looked like the aftermath of a hard-fought rugby international. We all traipsed through in a sombre single line with just enough time to consume some kiddush wine and a small piece of cake before the rain made it too soggy to eat. Not much simchah there!

True, if living in the succah causes us discomfort, we're exempt, but the very idea of leaving our nice warm comfortable houses and setting up home in a draughty booth doesn't immediately conjure up thoughts of simchah.

The message of the succah is that physical things don't buy us happiness. They can buy us fun - or more accurately they can rent it for us for a while - but there always comes the moment when the gilded carriage turns back into a pumpkin. Happiness, real happiness, lasts forever because it becomes a part of who we are. Real happiness adds to us. It makes us more than we were before.

In Tractate Succah, the Talmud mentions a measurement called a tefach sameach. A tefach is the size of a hand's-breadth. A tefach sameach is an oversize tefach. It's a tefach - and a little bit more. But, literally, it means "a happy tefach".

What were the sages of the Talmud hinting to here? Why didn't they just call it a "large tefach", or even a "maxi-tefach"?

The essence of happiness is to become more than we were without losing ourselves. The tefach is still a tefach - it hasn't become something else, it hasn't lost itself - but it's more than it was. Things that make us more, make us happy.

When we get married, our happiness comes from the feeling that we are now more than we were. When we have children and grandchildren, that feeling of expansion through the generations brings us yet more happiness. These are genuine moments of mind-expansion, where our little tefach-selves achieve simchah.

All true happiness comes from a perception of growing, and the greatest happiness is to grow spiritually, to feel closer to God.

The so-called psychedelic drug experiments of the 60s were an artificial attempt at achieving this mind-expansion, but apart from leaving an appalling human fall-out, the premise of the drug gurus was fatally flawed. They confused "getting out of it" with "getting into it". True Jewish simchah is about "getting into it", expanding our consciousness without losing ourselves.

Things only make us happy to the degree that we feel we possess them. It's a lot of fun to own a Bentley Continental but, at the back of my mind, I know that the Bentley Continental can always be separated from me - it can be stolen or break down - or I can be separated from the Bentley Continental. I have no guarantee that I will be in this world tomorrow. And that feeling stops me from really being happy about it, or any material thing for that matter.

Spiritual things, spiritual achievements, make us happy because they can never be taken away from us. They become part of who we are. And that's why they make us happy. We genuinely possess them.

That's the message of that little flimsy booth at the end of your garden: leave our comfortable homes! The physical world is great fun but it will never make us happy because it doesn't really add to us.

The essence of simchah is that we become more than we were without losing who we are.

Rabbi Sinclair lectures at Ohr Somayach in Israel; his website is at www.rabbisinclair.com