In Hindu religion, (actually, religion is full of beliefs ) there is a belief about marriage if a man ties a knot to a woman which means they are continuing their previous births relationship. To be precise, they both were husband and wife for the last 6 births. (No reprieve for a man as he does the same wrong again and again) .
Then what about "affairs" which does not result in marriages (come on yaar, affairs are meant to be to used as "the best time pass"). You enjoy some one get married to someone. That someone might have had a similar "affair(s)" before the marriage. The marriage completes the mere formality. that's all.
Then why have a high expectations about the marriage!!!!!!!