Noun. what you wear when you analyze events,or dissect previous errors, with the benefit of hindsight.

the thing that you don’t have when you’re phones percentage is over 20

The (usually rose-colored) glasses which one views the past. Viewing through retrospectacles causes one to overlook past problems or disasters and remember only the good aspects. Thus, retrospectacles are often the device which allows one to intentionally repeat the same ill-advised course of action.