It’s An Ugly Truth: The 8 Most Common Reasons People Cheat
But that’s a cop-out
If you are a good communicator, you should never feel that your co-worker, or anyone else, understands you better than your partner! Your partner should be the one that gets to lend you a listening ear, or a shoulder to cry on, or advice on your most trying times. If you feel your partner hasn’t been doing those things, it’s either because they’re a terrible partner (in which case, again, you should just leave them and if you haven’t you probably have codependency issues) OR because you haven’t given them the chance to.