One of the worst experiences in life is pretending not to know when you actually know. But I agree. Sometimes, it is best to pretend not to know when you know.
It is absolute torture to know that your partner is a cheater. It may not necessarily be cheating with another human being. It can take multiple forms. Like gambling, booze, facebook, friends or any activity that has reached the level of addiction, so much so that it steals that person away from you.
To sit in their company knowing they long to be somewhere else, to share their bed knowing their brain holds images of someone/something else, to talk to them knowing they have not heard you, to look into their eyes only to see them glazed by a memory you have not shared, that is absolute torture.
Because, inevitably, it kills your soul. You die a little each time you reach out to them and they move away, out of reach.
So you pretend. You pretend not to know that you have competition and that it won. You pretend that it does not matter.
Sometimes pretending that you don't know is all you can do to save your sanity. Forget dignity, righteousness, justice. You are fighting for your sanity. And the only way to do it is by pretending.