Out of the entire troupe of Our Lord’s apostles, even after three years of front row seats at miracles and sermons, only John was able to stand up and watch the actual events of the Passion. The others fled the sight, and it was undoubtedly a mercy for them to be able to shield their eyes.
Perhaps the horror of the Passion would have obscured for Andrew and Thomas and Peter the joy of the resurrection. Perhaps it would have irrevocably shaken their faith. Perhaps it would have led them into an anger and hatred that they would not be able to overcome....
But certainly, those same apostles who did fail to watch with him, lived and died with the certainty that theirs was a falling short. It was a failure of courage, and the consequence of a weak faith that kept them away from the images of Jesus on the Cross. Above all, it was proof of an imperfect love that ultimately placed their own safety and sensibilities over following Jesus....
People like to pick on the Apostles. I don't just mean people like Barbara; the Fathers of the Church picked on the Apostles, too. Heck, St. Mark makes them look about as sharp as a sack of wet mice, and he [most likely] knew some of them personally.
But although the Gospel is the story of a love beyond all dreams of excess, the Gospels themselves waste nothing. In the flight of the disciples from Gethsemane, the Fathers saw hope. St. Remegius wrote:
In this act is shown the Apostles' frailty; in the first ardour of their faith they had promised to die with Him, but in their fear they forgot their promise and fled. The same we may see in those who undertake to do great things for the love of God, but fail to fulfil what they undertake; they ought not to despair, but to rise again with the Apostles, and recover themselves by penitence.
But there's a deeper theological point to their frailty.
Yes, they had "three years of front row seats at miracles and sermons." This should have given them faith. But this faith was not sufficient because the miracles and sermons were not sufficient. It was only through Jesus' death and resurrection [and ascension] that the Holy Spirit, Who is sufficient, descended upon the disciples.
The lesson for us is this: If we attempt to be disciples of Jesus by our own power, we will fail. Our only hope for success -- literally, our onlyhope -- is to act by the Spirit we receive through Jesus' crucifixion. If we do, we will succeed. (Which, of course, entails a high probability of martyrdom.)