Maybe I'm naive....
But i expect that whoever I choose to marry someday to not allow themselves to get close enough to anyone to fall for them. Falling in love doesn't just happen....there are a series of choices and situations that lead to it that can be avoided if someone makes that choice (including but not limited to not having one on one time with anyone of the opposite sex, not having any kind of intimate conversation with members of the opposite sex, not confiding in or turning to anyone other than same sex friends, family and spouse for support, etc).
Again...I'm not married and maybe I'm stupid....but I think falling in love with someone else is completely avoidable.