When two pieces of wood are placed together in the shape of an inverted V, if each supports the other, both will stand; but if they do not, both fall to the ground. As this matter is one of such great consequence, try to look upon the defects of your companions as a kind of special medicine and a cross prepared for you by God. There are many people who willingly practice penances which they have chosen for themselves, but who refuse to put up with their neighbours’ faults, though that is the penance which God has chosen for them to bear.
Saint Robert Bellarmine