I was wondering what Jesus means when he says in verse 38 "It may be in the second watch he comes, or in the third,"
Jesus was using a metaphor. The comparison of this present life and world in which we live has been compared to night--a time of darkness that lacks light. We, believers, are in the Light of Christ even though we live in this present age.
What Jesus is saying is that no one knows when He will appear. In His time, guards watched from the city walls all night looking out to see if enemies approached. The second and third watch were in the dead of night when the least activity would be expected.