We use this expression to say that someone will benefit from trusting us or our opinions. It is common after asking for a favour.
You can use this phrase in ………… language.
A: So, would you like to work here?
B: Yes, sir. I’m good with numbers. You won’t regret it.
A: Why should I buy these shares? They seem quite risky.
B: They might seem risky, but they aren’t. You won’t regret it, I promise.