Weigh it out... do all of his other attributes carry more weight than this one offense? If they do, then put these worries to rest... if they don't then leave and spare both of you the misery of reoccurring doubts and insecurities.
"The weakest soul, knowing its own weakness, and believing this truth that strength can only be developed by effort and practice, will, thus believing, at once begin to exert itself, and, adding effort to effort, patience to patience, and strength to strength, will never cease to develop, and will at last grow divinely strong."
- James Allen