This is what Jesus said concerning His second coming.
Matthew 24:
42 - "Watch therefore: for ye know not what hour your Lord doth come."
43 - "But know this, that if the goodman of the house had known in what watch the thief would come, he would have watched, and would not have suffered his house to be broken up."
44 - "Therefore be ye also ready: for in such an hour as ye think not the Son of man cometh."
What are we instructed to watch for in verse 42? Obviously it is the coming of the Lord. He comes as a thief in the night, in an hour as we think unlikely. Thus we are instructed always to be watching. If we are watching for Jesus, understanding He could come back at any time, what is hard to fall into? Slothfulness. If we understand that Jesus could come back at any time, we cannot become lazy.
All you have to do is read the rest of the chapter, 45-51.
You can also see how this word is used elsewhere. Here are just three uses of the very same word:
Rev. 3:2 "WAKE UP! Strengthen what remains and is about to die, for I have not found your deeds complete in the sight of my God."
Rev. 3:3 "Remember, therefore, what you have received and heard; obey it, and repent. But if you do not WAKE UP, I will come like a thief, and you will not know at what time I will come to you."
Mark 14:34 "My soul is overwhelmed with sorrow to the point of death," he said to them. "Stay here and KEEP WATCH."
In that last one, for instance, He didn't mean for the disciples to be
lookouts, to tell Him when the betrayers were coming. He meant for them to
watch and pray, seeing that the spirit is willing but the flesh is weak.