His Infidelity is His Worst Regret.
The vast majority of people have a plethora of regrets as they reflect on their lives. They may have done or said things they later regretted or wish they hadn’t. The most important thing to remember about Arnold is that. Having the abilities of the Terminator, he could travel back in time and avert disaster if he so desired. That caused him to have the most regret in his entire life, because of the harm it did to their relationship and the possibility that it caused him to feel the most regret.
Even though he wishes he could, Arnold Schwarzenegger understands that he cannot change the past. Thus, he attempts to avoid dwelling on his mistakes and instead focus on what is to come. This doesn’t mean he can’t make an effort to do things right, even though he has previously made mistakes.