Is it okay to have an extramarital affair?

This, of late, I realised that it's a subjective issue. Where some consider it as an absolute sin, others think that it's all part of life, chance and emotions. What's your stand?

My personal belief is that in marriage no matter of what agreement it is, there are no two separate people, there is only one. So, if one half of your body objects messing up with another individual, the body as a whole should object it as well. But, if both halves are ok about it then I see no problem there.
I could never cheat and have no reason too, plus there is a very thin chance in hell that I would touch anybody physically for anything. I can like a person, even share time and do stuff together and I don't consider talking to be cheating at all, but I would not touch because for the rest I have the same thing at home.
You can tell that I am not romantic at all, so anybody even trying to drag me into some affair will soon come to an ugly surprise.
I am completely family oriented and I love only my daughter.