When I get upset I tend to tell myself “it doesn’t matter”. When people get angry they tend to tell themselves that the people they’re angry at “don’t matter”. When big things go wrong in our lives we tend to say “it doesn’t matter”. As if saying this over and over again will make it true, like it will take these things that obviously do matter and make them cease to.
It might seem harmless, but pretending things don’t bother you doesn’t make them stop bothering you, it just suppresses them so they can come back and bite you later. It’s why people bring up long past arguments in fights. Those things were never resolved, and yes, they’re still angry about them, even though the person they are fighting with has long since forgotten them. It’s a surprise to them, which normally makes the fight deteriorate at a rapid speed.
So yes, it does matter, it all matters. If you’re trying to dismiss something because you don’t think it should matter, that’s still something you need to dissect. If it shouldn’t be a big deal you need to figure out why it still feels like a big deal to you. Maybe you don’t need to get the other person involved, maybe it has nothing to do with them. If it is you, you should adjust, but if it’s them, or even a little bit of you both (which it normally is) you need to talk about it. Notice that I said talk, not scream, it’s normally best to calmly discuss things so you don’t end up attacking instead of resolving.