I remember my flatmate shifting uneasily. When I had left the flat the fridge had contained a Bakewell tart my sister had brought me during a visit. Now it didn't.

He didn't try and pretend the fate of the Bakewell tart was anything other than the obvious. The logic was basically that 'It was there and so...' He was embarrassed but unapologetic.

An apology would have been the right thing. Ideally followed by sourcing a new Bakewell tart. But that wasn't going to happen. Despite the fact that he was a decent guy and very intelligent his pride would not let him own his action.

Last week Martina Navratilova wrote an incredibly wise piece for the New York Times about Serena Williams' behaviour in the final of the women's US Open tennis final.

For anyone who's missed the story, Williams was penalised by the umpire for several violations of the rules, culminating in her calling him a thief, which contributed to her losing the match. She later accused the umpire of sexism and of punishing her more harshly than male tennis players.

Navratilova's article follows the reasoning that two wrongs don't make a right – that even if male players may have got away with similar behaviour, that behaviour is still wrong. As she puts it: 'I don't believe it's a good idea to apply a standard of "If men can get away with it, women should be able to, too." Rather, I think the question we have to ask ourselves is this: What is the right way to behave to honor our sport and to respect our opponents?'

In the heat of the battle, or at least in its aftermath, Serena should have been able to admit that her behaviour was wrong. But like my flatmate 25 years ago, her pride stood in the way.

Navratilova went on to say: 'We cannot measure ourselves by what we think we should also be able to get away with.'

The yardstick should be what is right, not what other people are doing or what manages to slip under the radar. We should be aiming high, not seeing how far we can bend the rules.

In the last couple of weeks, Boris Johnson and his wife have announced that they are to divorce. There appears no question that Boris has had a series of affairs during their marriage, leading to at least one child. What Boris has never done at any point when various accusations of this have been levelled has been to admit what he's done or to apologise – at least publically. Up till now his wife appears to have been willing to live with this behaviour.

There is a line of thought that says that what politicians do in their private lives should have nothing to do with their public role. This idea seems to suggest that the two can be kept conveniently separate and that behaviour in one area has no bearing on the other. I find this idea pretty odd.

Politics is not about fundamentally about politicians assessing evidence and making cold, calculated judgments about what is in the public interest. Politics is about people. It's about people who've got their shot at high public office, reacting to events and making a series of calls on what to do based on their interaction with lots of other people – ministerial colleagues, advisers, the press etc.

The point for me about whether they make good decisions is not expertise but character – things like whether they are willing to listen to others and think beyond self-interest. So, the question is whether I am happy to trust the fate of the nation to someone who has shown they can't be trusted, not because they are fallible but because when their shortcomings come to light they can't find it in themselves to admit them.

The Bible calls this stuff sin – the bit where we don't do the right thing and then compound that by not being able to admit we know we've done the wrong thing. As Paul wrote, we find ourselves doing what we know we shouldn't and not doing what we should (Romans 7:15). We all do it – we all miss the mark and fall short of the measure.

The question is always what we do next. Aiming high is not about being better than others. Aiming high is about knowing we can do better next time. That starts with accepting that what happened wasn't good enough. When I do that as a Christian I make progress not because of my virtue but because when I 'fess up I allow God to work in me to make me more able to get it right next time.

Dave Luck is the author of 'What Happens Now? A journey through unimaginable loss' and blogs weekly on www.daveluckwrites.co.uk. Follow him on Twitter @dluckwrite or on Facebook at the 'Daveluckwrites' page.