How do you stay calm when dealing with aggressive or unreasonable customers instead of matching their energy?

I help manage a service-based business and one area I know I need to improve is how I handle customer disputes.

Earlier today I had a difficult interaction with a customer. Looking back at it afterward, I can see several points where I could have handled the conversation much better. Instead, the situation escalated and eventually resulted in a negative public review.

The frustrating part is that I know what good customer service is supposed to look like when I'm thinking about it calmly.

My problem happens during the confrontation itself.

When someone becomes aggressive, accusatory, disrespectful, or very confrontational with me, I notice myself starting to mirror their energy.

Physically, I can feel myself getting extremely tense. Sometimes my hands/body start shaking, my heart is racing, and I can literally feel anger building inside me.

At that point I become much more defensive and focused on proving my side of the argument instead of thinking:

“What is the best way to resolve this situation?”

Then a few hours later, once I've calmed down, I can usually look back and think:

“I could have handled that so much better.”

I don't want to become someone who simply lets customers abuse me or agrees with everything they say. There still need to be boundaries, and sometimes the customer genuinely is wrong.

What I want to learn is how to remain emotionally detached enough to handle the situation strategically rather than personally.

For people who manage businesses, customer complaints, escalations, sales, hospitality, support teams, etc.:

How did you train yourself not to react emotionally when someone comes at you aggressively?

Are there any specific techniques you use during the conversation when you notice yourself getting angry?

Do you have rules such as never replying immediately, taking five minutes before responding, using prepared scripts, handing difficult customers to another person, etc.?

And how do you distinguish between:

standing your ground

versus

letting your ego turn a solvable customer problem into a fight?

I'm particularly interested in practical techniques you've actually used, rather than just “stay calm” or “don't take it personally.”

I know this is something I need to get better at, so I'm happy to hear criticism as well.