What had originally seemed like a clear-cut and soundly based decision can, after a few weeks or months, come under fresh scrutiny and inspire intense doubt, regret, shame, insomnia and, at points, hurried attempts to reverse a decision.

For example, a few months ago, it seemed absolutely right to end our relationship.

We had the partner's faults clearly in view, and we were certain that these made any sensible plans for the future untenable.

But now we're no longer so sure.

We've been on a few dates, and they didn't go too well.

We've been by ourselves a lot, and as we've been doing the laundry or walking around the park we've started to remember how funny and clever, sweet and tender our ex could be.

Still wondering whether we should, despite our original recommendation that neither of us should be in touch for a while, perhaps send them a falsely innocent text tonight.

Or, last summer we knew we didn't have a particularly good time at the beach-side resort, and vowed to stick to a cooler climate next time.

But since then the weather has turned very cold, and just recently we're finding ourselves curious about returning south next year.

Or, we told ourselves that we were fully done with a particular career, but we've been reflecting on matters since, and happened to bump into an old colleague last week, and are now wondering whether we shouldn't maybe make another attempt.

Or, a friend from university has suggested a meal.

We found them rather self-centred and dull when we last saw them a decade ago, but they sounded sparky in their invitation, and we've agreed to meet them for lunch near the station next week.

In such instances it can be useful to keep a broad principle in mind.

The further away we stand from the moment when we took a decision, the more our judgement is likely to be clouded and corrupted.

And this is because of a feature of our minds that in most areas serves us extremely well – our capacity to let go of pain.

The very faculty that means we can effectively mourn the death of a pet or a loved one, or get over a bankruptcy or endure a drop in income, also means that we are likely to revise our views of an ex we worked very sensibly to eject from our lives, or that we will know within five minutes of re-meeting an acquaintance that they are as maddening as they ever were.

We pick apart and dissolve our judgements because we cannot keep a clear eye on the powerful incentives we come under to do so, because we don't notice how indigestible certain truths have become.

We abdicate to doubt under intolerable, irrepressible degrees of loneliness and sadness, isolation and confusion.

Of course, we are going to start to question our views of our ex's strengths and weaknesses after seven weekends substantially on our own, being humiliated on dating apps.

Of course, we won't remember our friend's dispiriting character when we were so loved to have a flourishing social life.

When we wake up and wonder if we have been unfair or hasty, the sternest, most reasonable part of us should know to grab the controls and ask whether a revision to our views is likely to be accurate or simply convenient.

Despite all the pressures we are under to believe otherwise, we should place our faith in the wisdom of a well-worn dictum.

Trust what you knew then, not what you feel now.