I would dearly love to see the word "mistake" removed from any reference to a intentional and voluntary act. I have made mistakes - I've misread work communications, tried to grow pumpkins where no pumpkins should grow, and had many well intentioned but absurd creative moments in the kitchen. These are mistakes. I did not know in advance that my actions would cause harm or hilarity.
To conduct an affair is not a mistake. People don't unintentionally find themselves running out the Kama Sutra accidentally. People don't steal public funds unintentionally, they don't drive drunk unintentionally, they don't suddenly take up naked pole dancing unintentionally. Neither are these actions "errors of judgment". People don't think that having an affair could possibly be a good thing for their families but in this particular case it didn't work out right.
We need to get back to simple apologies if apologies are needed: not "I made a mistake" but "I callously thought I could conceal a red hot affair from my family and that it wouldn't impact my marriage. I was wrong."