In this verse, Jesus utilizes metaphors that pertain to His earthly ministry. In this context, "day" refers to the time remaining for Jesus to fulfill God's will on earth. "Night" refers to the rapidly approaching time when Jesus will die, terminating His earthly mission. The day is the most efficient time to work, but it is also a limited period of time. 
In His earthly walk, Christ had only a short window of opportunity to carry out the works of the Father Who sent Him. The Lord knew that every moment of His life was precious and should not be wasted. By His death, burial, and resurrection, Christ came into the world to be the Light of the World and to reconcile the world back to Himself so that all who believe in Him may be presented faultless and blameless before Him.
This is a wonderful example of what Christian living should look like. In complete submission to the Holy Spirit, we do only those things that are directed by Him. It is also a solemn call to accomplish the works of Him, who has called us out of darkness into His glorious light, knowing that our short period of time on earth is our only chance to serve the Lord well with what we have.

Dear Heavenly Father, thank You for Christ's example of a Man who accomplished the works of God and who lived according to Your will every moment of His life. As I follow His example, may I live my life in complete submission to Your Indwelling Holy Spirit. The night is coming when none of us will be able to work, so please give me the chance to share the gospel of reconciliation with others. 
In Jesus's name I pray. Amen.