Imitation of Christ

Gloria bonis hominibus testimonium bonæ conscientiæ. Habe bonam conscientiam et semper habebis lætitiam. Bona conscientia valde multa potest portare, et valde læta est inter adversa. Mala conscientia semper timida, et inquieta. Suaviter requiesces, si te cor tuum non reprehenderit. Noli lætari, nisi cum benefeceris. Mali nunquam habent veram lætitiam, nec internam sentiunt pacem, quia non est pax impiis, dicit Dominus. Et si dixerint: in pace sumus, non venient super nos mala; et quis nobis nocere audebit? non credas eis, quoniam repente exsurget ira Dei, et in nihilum redigentur actus eorum, et cogitationes eorum peribunt. 

The testimony of a good conscience is the glory of a good man. Have a good conscience and you will always have joy. A good conscience is able to bear exceeding much, and is exceeding joyful in the midst of adversities; an evil conscience is ever fearful and unquiet. You will rest sweetly if your heart doesn't condemn you. Never rejoice unless when you have done well. The wicked have never true joy, nor feel internal peace, for there is no peace, says my God, to the wicked. And if they say "we are in peace, there shall no harm happen unto us, and who shall dare to do us hurt?" believe them not, for suddenly shall the wrath of God rise up against them, and their deeds shall be brought to nought, and their thoughts shall perish.

Imitation of Christ, II, 6:1