"Keep your heart with all diligence, for out of it spring the issues of life." Proverbs 4:23 (NKJV)
One of the best things we can do is to keep a guard on our heart to be sure that the things we allow ourselves to be exposed to help us and don't hurt us. The Bible is very clear about our having the right kind of influences in our life and the results of having the wrong influences. By this I am not just talking about hanging around with the wrong kind of people and avoiding places that everyone knows to be a bad influence. Those kinds of things are certainly included, but from what I have seen and continue to see, many Christians are allowing themselves to be influenced by teachings and beliefs that are having a harmful effect on them.
One of the things I do in my ministry is to teach various classes in Bible schools. No matter where I might be and no matter what the topic of the class might be there is always someone there who has a question about something in the Bible. Very often the questions stem from something they heard someone teach somewhere. Then, because the person who asks the question is not sure what to make of that teaching they look for someone to help them understand what the Bible has to say about that thing.
No matter what we read or listen to we must be careful about what we "hear" because it will have an impact on us. Too often Christians just listen to anything that sounds good and they get themselves into trouble because of it. When we hear or read something we must always first check it with what the Bible says. If we cannot find clear Bible verses on the subject we should stay clear of it. If we don't do that we are not guarding our heart and the result will be confusion, doubt, and a hindrance in our relationship with God. We have to guard our hearts by keeping ourselves filled with the Word of God so that we will know what the truth is. If we don't we end up with problems that can send us off course in our walk with God. Guard your heart with the truth of God's Word and keep your relationship with God strong.