Answer: Haber de followed by the infinitive usually means "to have to," "to be necessary," or "to be supposed to," kind of like tener que or haber que, but expressing a much weaker and often vague sense of obligation. Although the expression is used a lot in some areas, in other places you're more likely to come across it in literature (or song lyrics!).
Here are a few examples of its use:
- Ha de estudiar mañana. She needs to study tomorrow.
- He de estar a dieta. I need to be on a diet.
- ¿Por qué habría de salir? Why should he leave?
Haber de also can express probability in much the same way that "have to" (or sometimes "must") in English can express probability rather than obligation:
- La solución al problema ha de ser difícil. The solution to the problem has to be difficult.
- Has de ser rica. You must be rich.
As to the song lyrics, here's one possible translation: "that good fortune will be my destiny and not something I have to strive for."

