what does " “live in day-tight compartments”"mean?
In addition to applying the principles discussed earlier in this chapter, we can effectively resolve complaints and build relationships and improve customer loyalty and retention by using the following eight-step process:
1. Greet. Always answer the phone or greet people in person as though you are happy to hear from them. Begin in a friendly way. This is easy to say, but can be difficult to do. We need to be able to “live in day-tight compartments” and separate any negative experiences from this customer contact. Even when the customer is a constant complainer, deal only with the current issue.

Question

what does " “live in day-tight compartments”"mean?
In addition to applying the principles discussed earlier in this chapter, we can effectively resolve complaints and build relationships and improve customer loyalty and retention by using the following eight-step process:
1.	Greet. Always answer the phone or greet people in person as though you are happy to hear from them. Begin in a friendly way. This is easy to say, but can be difficult to do. We need to be able to “live in day-tight compartments” and separate any negative experiences from this customer contact. Even when the customer is a constant complainer, deal only with the current issue.

Answer

Well, we get this expression from "watertight" or "airtight".

A watertight container doesn't let any liquid in (or out).

An airtight container doesn't let any air in (or out).

If you're wondering, these words are now familiar enough that we don't need a hyphen (originally, we wrote "air-tight").

So, a day-tight compartment doesn't let any influence from yesterday or tomorrow in. Also, whatever happens on one day isn't allowed to affect tomorrow.