It all happened so quickly. I had let Christ down even before I had stopped to think about it.

We had arrived at the hospital on the right day at the right time with a seriously unwell relative for whom a bed had been promised in a specialist unit. But once we got on to the ward, it emerged that no place was available after all.

I did not react well. And any thoughts of honouring Christ in how I behaved were far from my mind as I started to protest with what I can only describe as ungodly vigour and language. It was when I threatened to sit down and not leave the hospital until a bed was found – and the staff decided that I meant it (which I did!) – that 'somehow' a bed suddenly became available.

We had got what we wanted. But then it emerged that the main medic with whom we were dealing was not only a committed Christian; she had clocked from the paperwork that I was a church minister. I already knew I had let myself down in my reaction; now, with a deepening sense of shame, I realised I had let Jesus down as well.

And this brings us to Peter's betrayal. Or at least his confident announcement that he would never desert Jesus and let him down. As we continue our fortnightly pilgrimage through Mark's gospel we find the disciples, having had the Last Supper, journeying with Jesus to the Mount of Olives.

'You will all become deserters,' Jesus warns them (Mark 14:27), before citing an Old Testament prediction about it. 'Never!' is the gist of Peter's reaction. 'Even though all become deserters, I will not,' he claims. But Jesus is adamant: 'You will deny me three times.' Peter continues to protest – but we all know what happened. Within the space of just a few hours, Jesus' words would be proved absolutely correct.

The 'strongest' Christian, the best-instructed believer, the most famous and respectable church leader – all of us, without exception, are only a small step away from betraying Jesus or letting him down in some way, shape or form. And sadly we can all think of well-known public examples. What, then, should we take away from this disturbing truth?

1. Recognise your frailty. 'If you think you are standing firm, be careful that you don't fall,' warns the Apostle Paul in 1 Corinthians 10, having just listed the way some of our spiritual forebears descended into debauchery.

2. Remember your need of grace. The Christian life starts with recognising our absolute dependence on Christ and his grace – and it continues like that every step of the way. Some of the simplest and most helpful prayers are also the shortest ones: 'Lord, help!' or 'Lord Jesus Christ, son of God, have mercy on me a sinner,' are useful words to utter in times of temptation, testing and pressure.

3. Regard others sympathetically. Rev John Watson (1850–1907), known by his pen name Ian Maclaren, is thought to be the originator of the wonderful saying, 'Be kind, for everyone you meet is fighting a battle you know nothing about.' How true that is! Or as JC Ryle, first Bishop of Liverpool, writes while commenting on this section of Mark's gospel: 'Let us learn to pass a charitable judgment on the conduct of professing believers. Let us not set them down in a low place, and say they have no grace, because we see in them much weakness and corruption. We ourselves are all more or less weak, and all daily need the skilful treatment of the heavenly physician.'

4. Repent when you fall. There's a profoundly helpful section in part of an Anglican liturgy where we are asked: 'Will you persevere in resisting evil and, whenever you fall into sin, repent and return to the Lord?' I love the reality of that word 'whenever' rather than 'if'! And the answer? 'With the help of God, I will' – which not only shows us what to do, but also how to do it. Remember, however, that repentance is more than just 'saying the right words'.

Well, after I had sounded off in the hospital, the Christian medic took me for a cup of coffee. 'I'm sorry for how I reacted,' I said, shamefacedly, as we talked. The physician looked me directly in the eyes and held my gaze. It was some years ago now, but the moment which followed has stayed with me: 'I forgive you,' she said. And somehow her words and face simultaneously made me feel humiliated – for they conveyed the appalling truth of my failure – and yet also humbled, for the forgiveness she gave was offered with warmth. Just for that moment, in a quite extraordinary way (which the medic probably wasn't even aware of herself), I felt I was looking right into the face of Christ.

Failure was not the end of the story for me. It wasn't for Peter either. Don't let it be the end of the story for you.

David Baker is a former daily newspaper journalist now working as an Anglican minister in Sussex, England. Find him on Twitter @Baker_David_A The Rough Guide to Discipleship is a fortnightly series.