In this passage, part of Christ’s Olivet Discourse, Jesus makes a vital point for us.  We must always be ready for his return.

³⁶ “But concerning that day and hour no one knows, not even the angels of heaven, nor the Son, but the Father only. ³⁷ For as were the days of Noah, so will be the coming of the Son of Man. ³⁸ For as in those days before the flood they were eating and drinking, marrying and giving in marriage, until the day when Noah entered the ark, ³⁹ and they were unaware until the flood came and swept them all away, so will be the coming of the Son of Man. ⁴⁰ Then two men will be in the field; one will be taken and one left. ⁴¹ Two women will be grinding at the mill; one will be taken and one left. ⁴² Therefore, stay awake, for you do not know on what day your Lord is coming. ⁴³ But know this, that if the master of the house had known in what part of the night the thief was coming, he would have stayed awake and would not have let his house be broken into.  ⁴⁴ Therefore you also must be ready, for the Son of Man is coming at an hour you do not expect.

I have personally and unscientifically observed two common and unfortunate responses to the thought that Jesus can come back at any moment. 

One is to go completely overboard in end times enthusiasm.  I remember years ago having to comfort a man whose wife had died.  Grief is hard.  His was made worse by the conviction that he and his wife, who were not young, were both going to live to see the rapture of the church.  He has since died as well.  No rapture.

The other unfortunate response, perhaps egged on by views like the one above, is to decide that Bible prophecy is so difficult, obscure or controversial that it’s not worth paying it any attention.  This seems to be more common at present, but it directly contradicts Jesus’ point.

Whether one believes this passage from Matthew is talking about the rapture or not (I personally think it is, which I know is a minority view), Christ wants us to be ready.  He wants us to stay awake (v.42), be ready (v.44) and to watch (Matt 25:13).

The fact that we cannot know when Jesus is coming is not a motivator to not care when he will return.  I believe this tension and lack of clarity regarding his return is designed to keep us always watchful.  Every generation of Christians has every reason to believe that Jesus can come during their lifetime, but we can never be sure that he will.  

Therefore we must always be ready.  Let’s repeat that.

⁴⁴ Therefore you also must be ready, for the Son of Man is coming at an hour you do not expect.

Maranatha!  Come Lord Jesus!