It was a mistake for me to marry my XWW. Some would call it more than a mistake. Fine with me. But it was still a mistake.

One can make a conscious, thought out decision and that decision is STILL a mistake.

Contemplation of a choice doesn't guarantee one will not make a mistake and choose unwisely.

It certainly would not be correct to say an affair is NOT a mistake. I find that to be far more offensive, saying an affair is not a mistake, than calling an affair a mistake.

Again, mistake by no means minimized what an affair is. Just like hurt, the word needs qualification.

Stubbing my toe hurts, being betrayed by my spouse hurts as well. Just like we use the word hurt to describe both is no different than using mistake to describe the choice to have an affair, or to choose to eat too much.

Mistake is not a quantifiable term, so the scope and scale of a mistake requires a separate description.