Fred Clark, in yet another post lambasting the issues with the Left Behind series, also tackles a more general issue that is reflected in the novels:
This idea of God’s intensely specific individual plan for every detail of your life is a feature of American evangelical piety that we’d be better off without. It’s almost always a source of misery and almost never any help. It burdens Christians with anxiety over decisions that don’t need to be so fraught with moral implication. Choosing a major is hard enough without adding the notion that choosing “wrong” is tantamount to disobeying God.
Obsessing over God’s ISIPFEDOYL also tends to function as a way of distracting ourselves from “the weightier matters of the law: justice and mercy and faith.” If you’re worried about following God’s will, remember that it boils down to this: Love God and love your neighbor. That’s “God’s will for your life.” Take care of that and don’t worry about God’s ISIPFEDOYL.