The vices of which we are full we carefully hide from others, and we flatter ourselves with the notion that they are small and trivial; we sometimes even embrace them as virtues.

John Calvin (1509-1564) French theologian and reformer

The Institutes of Christian Religion [Institutio Christianae Religionis], Book 3, ch. 7, sec. 4 (1541) [tr. Van Andel (1952)]
    (Source)

Also reprinted in an extract as The Christian Life [De Vita Hominis Christiani], or, in the case of the Van Andel translation, Golden Booklet of the True Christian Life, ch. 2, sec. 4, subsec. 2.

The vices in which we abound, we sedulously conceal from others, and flatter ourselves with the pretence that they are diminutive and trivial, and even sometimes embrace them as virtues.
[Source (1813)]

The very vices that infest us we take pains to hide from others, while we flatter ourselves with the pretense that they are slight and insignificant, and even sometimes embrace them as virtues.
[Source (1984)]

The vices with which we abound we both carefully conceal from others, and flatteringly represent to ourselves as minute and trivial, no, sometimes hug them as virtues.
[tr. Beveridge (2008)]