Nevertheless, another worldly man that loveth his own worship and pursueth after it, if he love it not so much, that he would not for the getting or the saving of it do a deadly sin, or break charity to his neighbour, he sinneth not deadly but venially, more or less according to the measure of his love and of his liking, with other circumstances. (John Climacus)

The distinction Climacus makes between mortal and venial sins is suspect.

The doctrine suggests there are some sins beyond forgiving and others not so. The short distinction is between inclination and action. Short of action, most sins are venial.

But is not anything -- thought, word or deed -- sinful that complicates our relationship with God? And did not Jesus assure us of God's forgiveness of sin?