Of all the varied and wonderful joys associated with being married or in a long term relationship, there is one that tops them all in my book. When you are married, you have a built in confidante for life. It is true gift to have someone you can tell anything without fear of judgment or having it repeated to anyone.
Now sure, you could use that liberty to open your inner most thoughts and fears to another person who would understand and continue to love you anyway, but we all know that shit is what Tumblr is for. If you are doing it right in your marriage, you have complete and uninhibited freedom to indulge in copious of completely unrestrained-no holds barred-if anyone else heard you vocalize the fact that these are your actual thoughts they would never speak to you again... shit-talking.
When you are married, you talk so much smack about everything and everyone with your spouse that it practically becomes a sporting event (I hear they are looking to put inter-spousal gossip in the next winter Olympics). When you've been together long enough, it gets to the point where you can predict exactly what your spouse is about to say as soon as you've wheeled your cart a safe distance away from the worlds slowest and most socially distressing grocery store cashier in history.
I now automatically hold up one finger for silence when ending a phone-call I had on speaker because I can tell my wife is about to start talkin' some smack about whoever was on the line and she doesn't wait to make sure the call is safely disconnected first if I don't stop her. It's happened.
Every single one of us is at least a little bit of a judgmental piece of garbage on the inside, even if we don't vocalize it. When you are married though, you don't have to keep it pent up; You have an outlet for those innocent moments of pettiness and self righteousness that you know are wrong and make you a terrible person but you can't help having for just a second before you wave them off:
Those moments when you just want to yell at your Facebook friend Becky that she isn't fooling anybody with those mirror selfies where she is sticking her hips really far backwards to make it look like she has a thigh gap no longer have die quietly in your soul. You don't have to keep it to yourself that a mutual friend's new boyfriend has the personality of a house plant and you seriously considered getting up and turning his chair towards the sun to see if he would start leaning that way. You have someone to tell when the woman who runs the self check out area at Lowes and always gives you unsolicited, condescending pet care advice makes you want to shoot yourself in the foot with a nail gun just so the foot pain from your new nail wound will distract you from wanting to throttle her.
Getting those thoughts out safely and harmlessly in an environment where you nobody is going to judge you or spill the beans on what a dumpster-fire of a human you are is absolutely critical to mental health.
The alternative is to keep them inside and allowing them to fester and mutate into some sort of freakish calcified lump of petty bullshit that causes your organs to fail. In fact. I'm 98% convinced that, that's what kidney stones are.
Don't get kidney stones. Trash with your spouse. It's the responsible thing to do.