The following quote is from Mesilas Yesharim, more specifically, the chapter concerning the Divisions of Zehirus (Watchfulness). It is said that the Vilna Gaon would never leave his house before going over this chapter 12 times.
“A man should observe all of his actions and watch over all of his ways so as not to leave himself with a bad habit or a bad trait, let alone a sin or a crime. I see a need for a person to carefully examine his ways and to weigh them daily in the manner of the great merchants who constantly evaluate all of their undertakings so that they do not miscarry. He should set aside definite times and hours for this weighing so that it is not a fortuitous matter, but one which is conducted with the greatest regularity; for yields rich returns.” ~ Ramchal