Pessimism and optimism are characteristics of sinful humanity.  The one has no confidence for the future, the other over-estimates the combination of circumstances and ability (Proverbs 27:1).  True realism demands that we know everything about every interacting person, things and event.  That is information only God holds because there is nothing He does not know about the past or the future.  In these verses, Peter overestimated his ability to remain true to Jesus, even protesting His spiritual prowess and moral courage: his optimism was a hollow shell constructed in pride (Proverbs 16:18).

Denying the Word of God is the essence of sin.  Creating our own 'reality' is sin (James 4:13-17).  Here, Peter spectacularly proved the point.  Not only did he contradict Jesus, he also boasted of his own ability to stay true.  Jesus rebuked him with prophetic realism; accurately predicting the exact time of his failure the next morning.  But, as if to show us how self-centred and blind the sinful nature is, Mark then records Peter's emphatic denial of the rebuke he had received.  It must have been quite a moment for Mark to hear (who got his information from Peter in his later years), when the head-bowed bishop of the early church confessed his crass arrogance just hours before his catastrophic spiritual breakdown.

There are few more 'celebrated' Christian failures.  But, in fairness to Peter, he was not alone; all the others agreed with him. Alas, the self-propelled agenda of the proud heart, believing it can achieve anything it chooses, is all too much in evidence today (James 3:14). The professions of loyalty that melt into indifference, and the bold hand of faith that eventually shrinks from the task, are also still seen as wrecks along the Christian road. The fact remains, that apart from the grace and power of God available to those who stay close to Jesus Christ, we can do nothing (John 15:5).

Strangely, our best intentions may produce our worst moments - if we are not in line with the will of God and empowered by His Holy Spirit.  It remains a grotesque arrogance to pretend that there is no remnant of our sinful nature (Romans 7:18), or that somehow, we can do the work of God without His mandate or strength (1 Thessalonians 1:3).  Yet swarms of well-meaning Christian groups and churches are better equipped with information technology than prayer; and fleshly passion than holy submission.  Peter's mistake can be ours, and very easily too!  So perhaps this passage should be a reality check.