A Lesson Is Learned But The Damage Is Irreversible (ALILBTDII) is a webcomic drawn by David Hellman and written by Dale Beran. Ted Rall described the comic as "explor[ing] the limits of pessimism and fatal consequence in a universe that would be difficult to imagine on the printed page." David and Dale are the primary characters, although they do not appear in every episode, and there is a small cast of real-life supporting characters, including schoolfriend/mad scientist Paul, Dale's sister Sally, and David's mother, Debby Hellman (who dated the Devil in one strip).

Dale and David, who met at The Park School of Baltimore in ninth grade, published the first strip on July 15, 2004, and since then have produced more than 40 strips. New episodes appeared with varying frequency, sometimes weekly, monthly, or occasionally after a two-month hiatus. The comic was officially "on hiatus" from September 2006 to December 10, 2012, two more comics followed that hiatus and the last update to the comic was in 2013.