Remember with a vengeance, and you'll live with a penance.
Any wise person never forgets their past. Painful mistakes serve as vivid reminders - Rules of Thumb telling them what NOT to do. Drawing on that experience gives them strength, and allows them to be agile in the face of present adversity.
Others seem to search for mistakes to repeat. They fixate on possible outcomes, feeling it as though it were the present, and abandoning themselves to emotion. They embody the statement, "What is often mistaken for 20 years' experience, is just 1 year's experience repeated 20 times"
In short: Feel the pain. Never the malice.