As we talked earlier, must is used for a personal or internal obligation.

正如我们之前谈到的，必须用于个人或内部义务。

Have to Shows an external obligation and must shows an internal obligation to do something.

Have to 表示外部义务，must 表示内部义务去做某事。

We use have to for an external obligation and must for the internal or personal obligation.

我们用 have to 来表示外部义务，用 must 来表示内部或个人义务。

Although many use them interchangeably, in fact, we use " have to" for external obligations, and " must" for internal obligations.

虽然很多人会把它们互换使用，但事实上，我们用 “have to” 来表达外在的义务 （客观的），而用 “must” 来表达内在义务（主观的）。