Ever wonder why you friends gripe up in pain during a marathon only to sign up for another six months later? A new study has found the reason for this ‘selective amnesia,’ which allows us to block out painful memories associated with an event and instead thrust ourselves back in for another round. The researchers actually compare it to childbirth. Following the birth of their children, mothers’ memories of labor pain typically don’t match up to what they were feeling in the moment, which is attributed to their memories being ‘influenced by the meaning,’ says the study’s authors. The same holds true for marathons. When those positive feelings of accomplishment overtake the memories of blisters and calf cramps, you’re more likely to want to participate again. Do you find you also have this ‘selective amnesia’ when it comes to running marathons or competing in other arduous sports? Share your experiences in the comments.