Back in the times of kings, queens, counts, ladies and knights there was an expectation by these individuals and the rest of royalty to attend the Royal Court activities. Their attendance and contribution to the events of the day in court was their way of due diligence to the King and kingdom.
Today, two of the ways Americans show their due diligence is to vote and answer the summons to appear in court as a member of a jury. The dictionary defines diligent or diligence as constant in effort to accomplish something; attentive and persistent in doing anything.
When I researched the words diligent or diligence in Scripture, the references were to the consistent work on The Temple, not giving-up in your own personal faith journey (Heb. 6:10-12), being persistent with your gift from God (1 Tim. 4:14-16) and if you consider yourself a leader, then being steadfast in leading (Ro. 12:6-8).
The essence of diligence is summed up through Paul's words in his letter to the believers in Colossae. "Whatever you do, work at it with all your heart, as working for the lord, not for human masters, since you know that you will receive an inheritance from the Lord as a reward." (Colossians 3:23-24)
In this attitude and mindset presented by Paul we see wholeheartedness in anything and everything as the first key - "Whatever you do, work at it with all your heart,".
The second key is maintaining the perspective that whatever directive you are under from whomever, fulfill it as if it came from God - "as working for the lord, not for human masters,".
The last key is the why. You wholeheartedly work at anything as if working for the Lord because you know that you already are guaranteed a Holy Inheritance and will be rewarded for your diligence in good deeds through the Bema Seat Judgment of Christ (a judgment of the believers works or deeds for Christ while on earth that takes place in Heaven after the rapture) - "since you know that you will receive an inheritance from the Lord as a reward.".
The daily consistent meeting and walking with The Holy Spirit as a child of The King will develop this diligent mindset and attitude. Through prayer, focused thoughts on His Word (input), and screening our thoughts, words and actions through The Holy Spirit (output) - Christians will be on their way to doing their part in serving The King and kingdom effectively.
Jesus said that The Holy Spirit would be there for the believer to "teach you all things and remind you of everything I have said to you." (John 14:26). There is no shadow of a doubt then that Christians should look on themselves as Royalty with a purpose, but without the haughty attitude. The Lord says through Peter that through faith in Christ Jesus, believers "...are a chosen people, a royal priesthood, a holy nation, God's special possession, that you may declare the praises of Him who called you out of darkness into His wonderful light." (1 Peter 2:9) and we need to perform our Due Diligence.