Here is a letter from a pietist to his son
…in order to serve God faithfully at all times, remember that wherever you are God is with you, seeing and hearing everything you think, say or do. This thought will often keep you from doing evil and spur you on to do good; it will even be the reason for all the good you do…
Be diligent in your work, pay attention to everything and remember always that the profession you are learning now will not only be the means of earning a livelihood for the rest of your life but also that of serving God and your fellow man. Remember also that to a large extent, it depends on you whether you will be a useless person or whether you will amount to something in the world.
Therefore you must pray to God with all your heart for His Holy Spirit, and also expend all possible effort and care during your years of apprenticeship.
Courtesy World History: The Human Odyssey