Its hard for most people to come to terms with the fact that their partner has betrayed their trust. Seems to me that women forgive their partners more easily than men. Don't know how factually true that is though.

Coming to the question, I guess it depends on the mutual relationship between the couple. Whether there is a feeling that a mistake was commited and would not be repeated ever again. Whether for the greater good of the family, its better to work through infidelity.

I guess its just a very personal decision whether to invest more time in a partner that has commited infidelity. Perhaps, if you know absolutely that he/she loves you and that this was a one-off - maybe (just maybe) you can bring yourself to forgive.