While coming to consciousness from a dream this morning around 3, I realized it was one of those unusual, "different" dreams: this one of the return of Christ.
What was slightly disturbing was that the dream didn't seem to correlate with what I imagine Christ's return to be like.
Which isn't unusual, or even particularly different. The reality is that we have lots of ideas about the faith that we've picked up from various sources. Some are correct, some not.
A nuance of the Our Father's petition "deliver us from evil" is that we are praying that God would deliver us from error. Most of us who have gone through a somewhat checkered past theologically speaking have heard (and absorbed) lots of stuff that is perhaps wrong. So we pray continually against ourselves that God would correct our mistakes, dislodge our false opinions, and keep us from false teachers.
We can't do anything about false teachers we've listened to in the past. We can and should avoid them now. Which often means turning off religious radio or TV stations, avoiding error on the net, even avoiding much current religious pop music, which usually comes from a erring protestant side of the Christian faith. Taking note of our own internal mental conversation is also important. We need to notice how we think about God, what we believe, and how we react.
The importance of correct doctrine isn't so we can get a passing grade on some kind of quiz. It's that we might know God rightly. And knowing God rightly, we can the better trust Him, and rest on His mercy. That, perhaps, is the ultimate purpose in life.