I can always tell a relationship is about to be over when one person uses the phrase "You always x" or "You never x" or "Why do you always x" or "he/she is always x". It shows long brewing resentment toward the other person. Very funny if you're listening in, very scary if it's directed at you :)
Happens all the time in my marriage and still going strong. Sometimes you just accept the way the other person is, doesn’t mean you don’t point it out to them in moments of anger. But not necessarily a relationship-ending signal.