You have to be more careful/youust be more careful

[Rachel Adams]

Do native speakers use "have to" when the speaker's opinion is expressed?

In "English Grammar in Context" by Michael Vince I read there is a difference between "have to" and "must".

1. "You have to wear safety goggles." Is an outside rule.

2. "You must be more careful." Personal opinion of the speaker.

Can't personal opinion be expressed by "have to"? "You have to be more careful."

 

[Charlie Bernstein]

I agree with you. In those two sentences (lacking other context), "have to" and "must" are interchangeable.

In conversational American English, we usually use "have to."