Just because something isn’t a big deal to you, doesn’t mean it isn’t a big deal to someone else.
If someone tells you something is bothering them, listen. It’s completely okay to not understand. It’s not okay to belittle their emotions.
If someone snaps, ask if they are attacking you personally. If they are, that’s not okay. But if they’re just expressing exasperation or anger at a particular situation, try to listen.
If someone suffers from anxiety, then irritation or anger can be a sign of an impending attack, or of moderate to severe generalised anxiety. Anxiety doesn’t just present as nervousness or panic, especially in people that have to mask those feelings on a day to day basis.
Above all, make sure you’re not holding people to higher standards than you expect yourself to be held to. We’ve all experienced times when something mattered to us that seemed trivial to others. Remember that feeling, and use it to empathise when you face someone in a similar situation.
A big deal is always a big deal to the person experiencing it, whether you understand it or not. Be kind.