Have you ever had to drive on a familiar route, like on a road that you commute on, but you needed to make a different turn than you're used to doing? If you've ever driven to work when you meant to make a turn and go somewhere else, you've been conditioned! Conditioning can affect a great portion of your life - including your understanding of the Bible.
"Conditioning" is the process of learning something by repetition. We have an interesting phrase about this phenomenon: "Practice makes perfect." Actually, that's not entirely correct. Instead, practice makes permanent.
If you listen to any teaching long enough, eventually you'll begin to accept it. Then you'll embrace it. Then it will be your own belief. But what if that message isn't quite right... but you believe that it's right? That's the problem, and I see it all the time.
There was a discussion at church recently. One person in particular was trying to explain that Paul wrote the book of Hebrews. I mentioned that in fact no one really knew with certainly who wrote that book. But this guy stuck to his guns, insisting that Paul wrote it.
No matter what anyone said, he was determined that he knew without a doubt that Paul wrote that book. After pressing him for why he believed that, he finally gave us the answer: because for years my pastor has always said that Paul wrote it.
Now, this guy believed with all of his heart that Paul wrote the book of Hebrews. He had a belief based on conditioning alone, and he had no other evidence at all—just his conditioning. He had been conditioned so completely that he could accept no other possible reality, and yet he didn't really know why he believed it.
That was a tame example. There have been other episodes with fellow Christians (which I classify as "incidences") where people hold on to the craziest doctrines you can imagine. They are convinced that because these things were taught in a church that they are Biblical, so if you disagree with them, then obviously you don't read the Bible. And you don't love Jesus. So you're going to hell.
Practicing the right things makes the right thing permanent. But it's up to you to do your own homework and be like the Bereans, who searched the Scriptures to see "whether these things are so":
Acts 17:11 These were more fair-minded than those in Thessalonica, in that they received the word with all readiness, and searched the Scriptures daily [to find out] whether these things were so.
Having a zeal for God is not enough... it must be based in knowledge:
Romans 10:2 For I bear them witness that they have a zeal for God, but not according to knowledge.