The warning here is to beware of the "error of the wicked."  "The wicked" that he’s talking about is found in verse 16 and are the "unlearned and unstable" who twist the scriptures, and they do so to their own destruction.

In this instance he’s not talking about those who are obvious in their sin and rebellion against God.  He’s referring to those who make reference to scripture but yet twist it to their own opinion and ultimately to their destruction.  These are those who have a form of godliness because they are reading scripture and seem to be applying it, but they are incorrect in their application of it.  He says to watch out so you are not led away and fall.

When you see someone who is rebelling against God you know their thinking is wrong, but those who appear religious--who seem to be applying the scriptures--may look to be O.K. so you might accept what they say.  This is the reason the Lord has sent the Holy Spirit, so you can have the correct understanding and application of the scriptures for yourself--in your own heart.  Learn to follow His guidance in your heart.  It’s too important of a thing to simply take the word of others.

Confession:

I will be aware that there are those who, knowingly or unknowingly, do not correctly apply the scriptures.  I will be aware of these possible errors and learn to follow the guidance of the Holy Spirit.