Frustration is a function of expectations. We become frustrated, or discouraged, because the reality of what happens doesn't measure up to what we were expecting.
This is true for small things - as when an unforeseen traffic jam threatens to make us late for an important appointment. But it is also true for big things. Desperate actions, like suicide, adultery, or apostasy, often follow in the wake of a deep disappointment, a fundamental clash between the reality of life and our expectations for life.
Today Jesus wants to adjust our expectations. If we let him do that, it will be a major milestone in our spiritual lives.
In three different ways, today's Readings present us with a biblical metaphor for what human life in this fallen world really is.
The Psalm explains that God is faithful, that if we stay close to him, he will safely "show us the path to life, abounding joy in God's presence, the delights at his right hand forever."
The path to eternal life - that's the metaphor for what this earthly adventure really is. And in the Second Reading, St Peter tells us to "conduct ourselves with reverence during the time of your sojourning."
A time of sojourning, of journeying. We are on our way home; we are pilgrims heading towards heaven, towards our Father's house. The Gospel passage is a living parable for the same truth - Jesus walking with his disciples along the road to Emmaus.
That's was this life is - a pilgrimage, a journey, a path.
If we truly see life this way, as it truly is, we will expect what pilgrims expect: joys and adventures, yes, but also hardship, danger, and suffering.
But if we expect somehow to achieve perfect happiness with no hardships here and now - then we open the door to constant disappointment, frustration, and deep sadness.