Think no vice so small that you may commit it, and no virtue so small that you may over look it.
Confucius
The cardinal virtue of a teacher (is) to protect the pupil from his own influence
Ralph Waldo Emerson
Any of us can achieve virtue, if by virtue we merely mean the avoidance of the vices that do not attract us.
Robert S. Lynd
To many people virtue consists chiefly in repenting faults, not in avoiding them.
Georg Christoph Lichtenberg
Virtues are dangerous as vices insofar as they are allowed to rule over one as authorities and not as qualities one develops oneself.
Friedrich Nietzsche