Chapter 1: A Short Trip to Yesteryear
Ralph tends to block out his previous failures like the outcome of the Inter-Dimensional Derby - if he didn't easily forget the (numerous) times he lost, he wouldn't continue his quest for world domination! His stubborn determination is probably one of his only redeeming features.
Gyrode specifically references Ralph's patricidal scheme from the IDD, and we see that despite being ignorant of previous failures, Ralph does realise that he tends to foil himself. Never cross your own time stream, especially while holding a loaded gun!