Perhaps boredom and complacency in the marriage could cause one to fall for someone else.
couldn't agree with you more, happened to me
In my opinion,if you fall in love with someone else,be with them,beacous in reality,you didnt love the first person.
When someone else gives you something that you are not getting at home. Then you realize that you have forgotten how important that is to you. Whether intimacy, shared interests and so on. That is what happened to me. I had no idea I was missing something in my marriage. Until this other man gave me what I needed..
Throughout out lives, we change... first we are someones daughter, then someones friend, then spouse, then mother, At that point... we lose ourselves in taking care of our families, in being carpool mom, and cookie mom, and bandaide mom, and maid and all those other roles that take up every waking minute so that if we get 15 minute for a bubble bath we feel like we won the lottery.... (or maybe its just climbing the corporate ladder, but whatever filled your life to this point). At a certain point, those roles start dropping off... when our kids have become independent, or when our career is secure in where it is going, and we find ourselves with time on our hands... wondering if there has to be more in life, or maybe just feeling empty wondering where our value comes from now. It doesn't mean you value what you have less... just that you need something else to fill a void and to make you feel sexy and vital and important... like you matter.
But thats just a theory, i've never been married.