Halakhah for Moed Katan 9:14

Its laws are also short. Its content is generally that a man choose for himself in all of his matters and in all of his actions - whether in eating, drinking, [commerce], words of Torah, prayer, conversation or in any other thing - the good and moderate path; and never to remove himself to the extremes. And about this general principal, they, may their memory be blessed, said (Sotah 5b) that a man always examine his dispositions - meaning to say that he think about his affairs, to do them in the moderate and good path. And they based this upon a verse, as it is written (Psalms 50:23), "and to him who orders his way, I will show him the salvation of God" - they expounded (Moed Katan 5a), 'Do not read it [as] "and orders (vesam)," but rather "and evaluates (vesham)."'