like say if a women find a man she desires and want to get married to. obviously relationship will get rocky, not every day is butterflys and someone new can walk into her life that may give her more attention, gives her the butterflys whether is a coworker, colleague, or boss , a friend of a friend or whoever she comes into close contact with. On the most basic human instinct, she will enjoy the new attention, she will start questioning her own relationship, she will view the new guy with rose tinted lenses and bam all it takes is maybe a sip of alcohol or the jitters to consume her.

Even worse if you are in the relationship with her and you suddenly lose your hair, gain a bit of weight, lost your job etc.

lets say you take care of all that. Obviously there will always be someone bigger , better, stronger, more intellectual, more humorous , more adventurous , more money, more famous. Like if drake all of sudden walk into her life. why would she turn him down