Throughout the Gospels Jesus talks about “watchfulness” and its importance in a disciple’s prayer life.
This aspect of prayer is highlighting in the Catechism of the Catholic Church‘s section on prayer:
In Jesus “the Kingdom of God is at hand.” He calls his hearers to conversion and faith, but also towatchfulness.CCC 2612
In particular there are two ways a disciple of Christ can be watchful. The first involves keeping watch for Jesus’ second coming:
In prayer the disciple keeps watch, attentive to Him Who Is and Him Who Comes, in memory of his first coming in the lowliness of the flesh, and in the hope of his second coming in glory.CCC 2612
We do not know the day, nor the hour when Christ will come again and so we are called to “keep watch,” looking forward to when Jesus comes again.
The second way of keeping watch is through an attentiveness in prayer, realizing that the devil “prowls” about seeking someone to “devour”:
In communion with their Master, the disciples’ prayer is a battle; only by keeping watch in prayer can one avoid falling into temptation.CCC 2612
Whenever we pray we need to “keep watch,” looking forward to Jesus’ second coming, as well as being attentive to the deceits of the Evil One.