One of the great things about babies is that they don't dwell on the past. Nor do they hold a grudge for single incidents. A baby can scream for hours on end on account of gas just to have the whole experience vanish into thin air (pun intended) at the moment of release. Chances are that the baby immediately breaks into a smile, unless something else is still bothering him or her. A father can accidentally scrape her daughter's head on a wall while going through a door and have her forget the incident in about sixteen seconds. That's what I call cutting a struggling Dad some slack.
It's the positive experiences that stick. I guess it's got nothing to do with the inherent nature of positive versus negative experiences, but as a parent one can stop a negative incident from happening again, effectively making it an isolated incident. The good stuff, on the other hand, can be repeated over and over. Talk about a forgiving deal.
(The aforementioned incident involving a baby's head and a doorframe is purely fictional, although it may have happened to a father not entirely unlike the author in a parallel universe not entirely unlike ours. Do not reproduce said incident at home. No babies were harmed while writing this entry.)