God is light and there is no darkness in Him. When Jesus came into the world, He brought the light of Deity with Him. Now, after having listened and believed, we may become saints of the day. Since we are of the day, we ought not sleep. Sleeping refers to dark, morally shady, and evil actions. This kind of darkness shrouds our thinking so that we do not perceive the realities of evil and the coming of the son of Light. Jesus said "Work, for the night is coming." As children of the light, we ought to work, letting our "lights shine so that when men see [our] good works they shall glorify [our] Father who is in heaven." (Matthew 5).
How shall we stay awake? By letting our eyes be focused on Jesus at all times. Don't you find it hard to sleep when your eyes are looking right at light? Just so, Jesus said that our eyes are the lamp to our body. If our eyes are light our body shall be light. Paul said "Set your mind on things above and not on things below." (Col 3). If we will be sober, alert in prayer, mindful of the coming of Jesus, then His coming shall not take us by surprise, we shall not be found sleeping, and we shall be ushered into that final rest.
Working