We are all capable of treachery, of failure. The disciples were all so certain they would not deny Jesus, Peter in particular (Matthew 26:31-35). Jesus was the shepherd, and when he is struck, his sheep scatter. It wasn't unusual for Messiahs to appear, claiming to be king of Israel. It was also usual for the leaders to be executed and the movements to peter out afterward.
Jesus predicts the first part of this - that he would be struck down, and despite their claims, they would fail. And yet the end would be different, for Jesus would 'go ahead of you to Galilee'. This was all pretty real and raw for those who feared death, thought it was all over, and were then in for the biggest surprise in history.
For us today, while our faith is based on something we can look back at in history, and can be confirmed in our lives, there are times when it all falls apart, and it seems like Jesus has disappeared from our lives. Yet, he has promised to go ahead of us. And this we must hold on to.