"Slaves, obey your earthly masters with respect and fear, and with sincerity of heart, just as you would obey Christ." NIV translation
The discipline that we learned as a child prepares us to enter the workplace as an adult. This verse is telling us that we are to listen to our bosses and do our jobs as if our bosses were Jesus. A Christian should be the best worker at any job that there is and that brings glory to God.
We are to obey our earthly employer whether he or she is watching us or not because it is God's will that we glorify Him in everything. This is a reminder that we are to do the right thing because it is the right thing and not for earthly gains.
"Serve wholeheartedly, as if you were serving the Lord, not men, because you know that the Lord will reward everyone for whatever good he does, whether he is slave or free." NIV translation
Because we understand that we work for the Lord, whatever we do, we are to give it our best effort. Just as a worker gets a paycheck, we are going to receive a reward for the good that we do on the earth. This is also talked about, in Revelation 20, when the dead are judged.
"And masters, treat your slaves in the same way. Do not threaten them, since you know that he who is both their Master and yours is in heaven, and there is no favoritism with him." NIV translation
This discipline (basic training) extends to those who have been blessed by God with the authority over others in the workplace. If you are a supervisor, owner, foreman, etc. then you are to treat those under you (slaves) as you would if Jesus came to work for you. After all, He is the Boss (Master) of all. Brothers and sisters, if you are in a workplace that you hate, then introduce your supervisor to his Master and then show him/her this passage of scripture. Jesus can change anyone and it could become the place where everyone would like to work.