I'm planning to sleep with my wife's best friend that night.
Wow! Why test the water of infidelity and cheat on your wife?
Well, she might be sad but that's her problem not mine.
You shouldn't be doing things like cheating with your wife's friend. It is trouble and can cause great pain for both parties.
I bet my wife will not care. I want to fuck this chick.
You are in a monogamous relationship with your wife and stepping out on her with her friend is not correct. This foray into the world of infidelity is going to cost you your marriage if you are not careful. Don't do it.