In the context of customer service and irate customers it actually has two meaning.
The Self-Control Cognitive Meaning
Over the last decade or so, Psychology has advanced a lot by focusing on our self-talk and what we say to ourselves. In many ways, what we say to ourselves dictates whether OUR emotional reactions to a situations are negative and positive and whether our feelings escalate or calm down. The principle "What you focus on, you get more of" tells us that if we mentally focus on, and label customers negatively, we're more likely to get angrier. It's really about what you focus your attention on, and that's a key to controlling your own emotions.
Example: For most people, after a rough day with a lot of difficult customers, there's a tendency to rehash, rethink, and FOCUS ON the bad parts of the day. The more focus on the negative aspects, the angrier they can become. Not everybody does that but it's common. Contrast that with people who "let go" of the day, and don't focus on it. They will end up less stressed, and readier to take on the next day.
This applies WHILE you are interacting with a difficult customer.
The Second Meaning - Focusing DURING INTERACTIONS With Customers
In any conversation both parties forge the direction of the conversation through what they say to each other. With irate customers it doesn't always feel you have any influence, but you do. What you say will have some effect on where the conversation goes. So, if you focus on the highly emotional feelings of an irate customer, you're probably going to spend MORE time on discussing them, than if you acknowledge them quickly and move on.
Example From A Government Situation
Let's say you work for government and a customer starts talking to you about how much he hates government. One response you could make is to ask "Why do you feel government treats you so badly?", in the hope that expressing interest in what he is saying would work. In effect you FOCUS on the topic, and you WILL get more of it. And it's not constructive since you can't help the customer while he's ranting on and on.
A better response within the CARP system is to acknowledge it, then refocus on why he's actually talking to you, and how you might help, or determine you can't help. Like: "Some people aren't very comfortable with how government works, but let's see what I can do for you right now". You acknowledge without really encouraging, and you FOCUS the customer to go in a different direction.
In the following video from our free video seminar, you can learn more about the issue of focusing on the wrong things with angry customers, AND the importance of defusing early.