I am slightly confused by what you mean her mikemissmoe? You seem to imply that you have problems being faithfull, am i right? Trust and being faithful are the most important part of any relationship in my opinion.
This is probably not the answer you are looking for,or I am not understanding the question right.. But I would say: because love is supposed to be free..and you can never lock it down..But fortunately or unfortunately it comes with conditions and be faithful to each other, is the the main condition.