Sometime enough time and effort is put in when making a decision, but it can still be a bad decision for numerous reasons, you have to pick the lesser evil. If person A is staying with person B just because they dont want to hurt B, then A is denying themselves happiness. Like I said if you can live with the guilt of having caused someone pain then go ahead, if you cant then do whatever you need to do to make things right. Whatever you decide at the end of the day, you only need to answer to your conscious.