'Truth' can mean different things, such as facts, conformity to reality or actuality, a true statement, or the quality of being correct. Jesus, as the Son of God, personified truth, and everything about Him was true. As those who are following Him in order to become like Him in His character, we also need to become more and more true in every part of our life. For example, hypocrisy and pretence should be disappearing more and more.
2Th.2:1-12 speaks about the coming of the Antichrist who will try to deceive people by pretending to be true, even to the extent of claiming to be God himself, and win them to his way. While people assume that they are following the true God, he is actually leading them against God. This deception is already at work, in a smaller but increasing manner, through many preachers who are being influenced more or less by the spirit of the Antichrist. When people listen to them, it seems to them that they are listening to messengers who are bringing them 'light' (2Co.11:14).
Paul tells us that for us, what we need to take care in order to avoid getting deceived is to love the truth (2Th.2:10). When we listen to preachers we may think we want to understand the truth, and so, like the people of Berea, we may be even taking steps to verify if what these people preach is according to the Bible (Ac.17:11). That is necessary, but not enough. What we see here is that we also ought to have within us this 'love for the truth'.
Imagine if we are trying to hide or excuse some sin in our life. Then when we read the word or listen to it, we would be very keen to find something that would justify or excuse our sin! For example, we would be delighted to hear about how rich and wide God's love and grace are towards us, and imagine that God will just overlook our sin. Haven't we deceived ourselves here? If we really love truth, we would acknowledge our sin, know that it is totally opposed to God's character, and beg God for forgiveness and help to overcome. So we see how it is also our response to truth or reality that decides whether we would be deceived or not.
Deception is becoming more powerful and common, and it is a real battle for us to discern what is true and what is erroneous. Getting to see this error is not just about whether the preachers can back it up with Bible verses, but also about whether this teaching will lead us to victory over our sins and becoming more like Jesus. To be able to do that, we should be very clear about where we stand with respect to sin in the sight of God in terms of practical reality. Instead of finding cover for our sins, we should be willing to stand completely open before God and allow His Holy Spirit to bring light into our hidden areas so that we can repent.
There is a powerful trend in the world telling people to think good about themselves and avoid negativity. We should overcome this, and become real before God if we want to be saved from deception.