Someone once quipped: "Promises are like babies: fun to make, but hell to deliver."
There is a lot of truth in that.
Promises can be fun to make.
Imagine that your friend is unwell and cannot leave the house.
She seems lonely and depressed, and so you promise to stop by each evening on your way home from work.
You find it very pleasant to make the promise.
After all, in doing so, you are demonstrating what a loyal and caring friend you are.
You get a lovely warm feeling inside.
But keeping the promise, well, that is another matter entirely.
The trouble with a promise like that is that it is so long term.
Keeping a promise to visit your friend tomorrow is eminently practical and doable.
But a hasty promise to keep on visiting your friend can become an impractical burden.
You either wear yourself out trying to keep it, or you disappoint your friend by breaking it.
This is what the American self-help writer Norman Vincent Peale, author of How To Win Friends And Influence People, had in mind when he said: "Promises are like crying babies in a theatre: They should be carried out at once."
If a promise cannot be quickly carried out, it ought not to be quickly made.
I once made a promise that was neither fun to make nor to keep.
When I was a boy in England, I joined the Boy Scouts, now the Scout Association.
Part of my initiation was to take the "Scout Promise".
It went like this:
"On my honour, I promise that I will do my best
To do my duty to God and to the Queen,
To help other people
And to keep the Scout Law."
Being a sensitive and rather intense child, I felt uneasy about this, because I regarded it as a promise I could never keep.
There would be times, I felt sure, when I would not only fail to do my duty, but also fail to "do my best" to do my duty.
I sometimes wonder if any Boy or Girl Scout has consistently managed to do their best to do their duty.
If so, they deserve a really big badge.
On the whole, I think that promises, like marriages, ought not to be "entered into unadvisedly or lightly".
The Book Of Judges, in the Bible, tells the story of the very rashest of rash promises.
Jephthah of Gilead - so the story goes - was chosen to lead an army of Israelites against their traditional enemies, the Ammonites.
Before the battle, he swore an oath to the Lord that if he were victorious, he would offer up, as a burnt offering, the first thing that came out of his house to meet him upon his return.
Unfortunately for him, the first thing that came out of his house was his daughter.
Unfortunately for her, he felt obligated to keep his promise.
In a truly heartrending passage, she asked him for two months' reprieve, "that I may go up and down on the mountains and weep for my virginity".
Generally speaking, we ought to keep our promises.
People rely on us to keep our word, and feel let down and unvalued when we fail to do so.
But sometimes, when we have made a promise that was thoughtless and impractical, or one that no longer fits the reality of our lives, we can be left with no reasonable alternative but to break it.
At such times, there are a few golden rules.
• Be upfront about it. Admit that you made a promise, and admit that you are breaking it.
• Try and find a way to honour the spirit of the promise, even if you cannot follow through on the details.
• Think twice before you ever make that kind of promise again.
• Gary Hayden is a philosophy and science writer.