As I write on Sunday at noon, this country is making history – the first ever public rally against antisemitism, backed by the Greater Manchester Bet Din, and including the present Chief Rabbi of the UK as speaker, together with MPs from all over the country.

This national event took place here in Greater Manchester, just two miles from where I was born and in the very street where my Holocaust immigrant father started again: from being a young judge in Poland (where the rest of his family were murdered) to adapting to a new country, a new language and a new profession as textile wholesaler in the city of raincoats.

This Sunday rally outside the Anglican cathedral took place during the in-between period when we Jews have have, since records began, taken the time to introspect on our lives and failings, hoping by so doing to return to G-d.

For last week, on Rosh Hashana (the Head or Beginning of the Year), we were inscribed in G-d's book and beginning on Tuesday evening, Yom Kippur, the Day of Atonement, our fate will be sealed. But our 'return' is always possible and if genuine our own return returns G-d towards us and the decree against us is thus averted for another year.

Judaism regards every person as of equal value. G-d told Adam, the first human being, 'There is nowhere you can hide: I know all your thoughts.'

So what we have to examine in these 10 days of penitence is not how others behave, but how we behave – and I'm not talking about the 'sins' of eating bacon sandwiches or mowing the lawn on Shabbat. Those kinds of mitzvoth (precepts) are easy enough to keep if we really want to and set our minds on them. Often we even keep these precepts by rote, without even thinking.

What is far more difficult is how we deal in our daily lives with the people we encounter. Do we treat our children with respect, even when we disagree with them? How do we treat the plumber, the electrician, the home help (if we have one)? What about people encountered in the street who are lost, foreign, or unattractive in various ways: do we treat them as if they are in G-d's image, as Judaism teaches, always and everywhere?

Or do we simply take advantage of people and discard them when they aren't of use any more?

If people let us down, as they tend to do, how do we respond – do we let people down ourselves? Would it not perhaps be better not to expect anything of others and then often be pleasantly surprised?

The point of 'returning to G-d' is to reacquaint ourselves with the source of our existence. We should not allow the mitzvoth to take us over to the extent that we end up mistaking the trees for the wood. And the wood in this case is G-d himself, that intangible being whose ways are different than ours and whose thoughts are not our thoughts.

For the relationship we have with G-d is unique and the mitzvoth are simply the means of getting there.

Of ultimate importance in Judaism is commitment. Committing ourselves to change and immediately acting on this commitment in the new year of 5779 is more essential than ruminating on the bad habits and worse of the past year of 5778. But the past is also important. Having committed to starting again for the New Year, we should nevertheless use our 'sins' of the past year to turn ourselves into a more profound person who transmutes rather than represses.

For every mistake we make throughout our lives helps us to learn.

And the worst thing possible is depression. As Winston Churchill, who admired Judaism, said: 'Success consists of going from failure to failure without loss of enthusiasm.'

This could be the motto of the Jewish people: 'Be bold; take risks. You will fall by the way. But through your fall you will rise and I, G-d, will help you.'

Sitting on the fence is simply never an option.

As the great Jewish mystic and Chief Rabbi of Israel, Rav Kook (1865-1935), wrote in his seminal work The Lights of Teshuva: 'Timidity is an evil trait. It is the dross in the fear of G-d. Until timidity is purged from it, the true awe of G-d will not be crowned with love and joy.'

Two images spring to mind: the orange and the dress.

As I was walking to Shul yesterday – which is known as the Shabbat of Teshuva (Return), I tried to define for myself what Judaism is at core.

Judaism can be compared to an orange. With an orange, it would be advisable to take your time. You peel the skin and carefully recycle it. You take a knife and cut the peeled fruit into segments. You remove any pith or pips (and similarly recycle). You take one of the segments of orange in your hand. You chew slowly and carefully to avoid bits going down the wrong way. And at the end you feel quite full and have absorbed your recommended quota of Vitamin C for the day, together with added ingredients whose health benefits are essential but not always easily definable.

But why, you might think, take the trouble to go through this tiresome and time-consuming ceremony when you can obtain the same results by simply pouring yourself a glass of orange juice? Surely, in our busy world, this is the optimum solution, with the same benefits, and much easier for the children.

Alas, no. We now know that juice in large doses is actually bad for us. Even if we occasionally buy the more expensive juice with 'bits' to make it seem that we are doing the real thing, we are simply drinking a dilution which, at the end of the day, often rots our teeth – or so my dentist tells me.

The word for 'teeth' in Hebrew is the same as for 'year' as in 'Jewish New Year'. They are both related to the concept of 'repetition'. On Jewish New Year we should be cutting our teeth on the real thing and not simply putting up with second best.

In the biblical book of Leviticus, the injunction to love your neighbour (for instance) is surrounded by examples of how best to love and how not to love. But for the last 2,000 years the non-Jewish world on the whole has preferred to dilute this teaching, preferring the juice to the orange itself. After all, isn't the watered-down version so much easier to absorb than the whole – but what about the long-term consequences?

As I was returning from Shul yesterday, carefully digesting one uplifting sermon after another, I espied a friend across the road. This friend has been through loads in her life. But there she was in a new outfit of bright scarlet, replete with hat and feathers. I had to hand it to her.

My friend is a teacher at an ultra-Orthodox Jewish school in our neighbourhood. And being a person steeped in Judaism, she must be aware of the famous passage from Isaiah (1:18): 'Though your sins be as scarlet, they shall be as white as snow.'

But even the prophet Isaiah wasn't going to stop my friend enjoying life to the full – even during the time of return. For isn't it the case that returning to G-d means demonstrating to the world that Judaism always chooses life – whatever the circumstances? And if it means wearing a scarlet outfit to Shul on the Shabbat of Teshuva, so be it!

Dr Irene Lancaster is a Jewish academic, author and translator who has established university courses on Jewish history, Jewish studies and the Hebrew Bible.