What I'm about to share are observations I made on my own, and when I experimented (which I refuse to recommend doing). My experiment went something like "[someone I respect] said that when she listened to [a non-Christian radio station of which I cannot remember the name] she began to notice subtle attitude changes: sassy-ness, bummer moods, lashing out at people, and so forth. While I believe her I think it was just her, that won't happen to me - so I'll give it a go. Besides I haven't been forbidden to listen to "secular" music like she had been, so I won't be disobeying like she was." Yep, not a good experiment.
So I watched as many movies as possible, no sneaking around or anything, I just watched movies with my family and tried to promote movie-watching. "Hollywood junk" put into the movies wouldn't affect me, and anyway we were always really careful about what we saw. I also surfed the radio and I changed the station whenever a "bad song" came on (in other words if there was cussing). Fool I was. There was definitely a change in my attitude. Sometimes it showed in person, but it was mainly in my mind. In the thoughts I thoughts, what I meditated on, and I was generally in a "down" state of mind. I decided, "well, maybe all of this actually is affecting me aversely. So I'll quit" (which was easier thought than carried out). My attitude did see an improvement. I thought that was curious, but didn't pay much attention to it after that.
That was my experiment. My observations have been made by looking back on my life, and recently seeing how the various things I do have affected me. I've noticed several things.
(1) Songs, but particularly movies and books (as in novels/classics) that do not have some kind of romance are extremely rare. I can think of one or two movies off of the top of my head that do not have this ("End of the Harvest," which is more apologetic oriented, and "MVP") and about the same number of books ("Peloponnesian War by Thucydides, a history book, well, some of the others I would use as examples could probably go either way. hmmm).
This does not help for a pure thought life. Outside of the Christian radio scene this is also a pretty common theme. In fact, I constantly have to change the change the station for this reason. Country music I have to change the station for least of all (sometimes I can get 3 songs in a row that I don't have to change the station for! How sad). A little less than half of the time of the Christian stations you can't tell if they're singing to God or a girl/guy, a little less than half of the time there is no substance to what is sung, and the rest of the time there's actually something I enjoy listening to. I don't listen to any radio a lot anymore. I digress. So romance/love/lust is hard to avoid.
(2) Violence is seems just as hard to avoid. I don't know about you, but seeing acts of violence disturbs my thinking. It's like that scene gets stuck on "replay" in my brain, it's hard to get out. There are many movies I cannot watch because I know they will develop unhealthy thought patterns. Thankfully I realized this early on, unlike the whole "romance" thing. Songs about violence are prevalent; thankfully I don't even have a desire to hear those anymore. What you hear does affect you. Reading of violence in books rarely disturbs (if it's in a war situation, other violence sometimes does. Thus I have to be careful what I read and how much I read of it).
(3) I enjoy reading more than watching movies, or even listening to music. I have found that if I read a lot without reading a lot of the Bible my outlook on life becomes gloomier. For instance, I read Crome Yellow, Wuthering Heights, and Work within three days, I believe. I read some of my Bible, not a lot though. I was so down and I couldn't understand why. I eventually figured out that I was overemphasizing the "secular" works. Not that you need to "balance" and read equal amounts of Scripture to non-Scripture reading, but it is good to saturate your mind with the Bible to make sure you don't allow the other to take root in your mind.
So be careful what you see and what you hear and what you speak of - it does matter. Just because someone else may not be able to see that your thought life changes when you read/watch/listen to certain things does not mean that it is of no value. It is. We are to love God with our heart, soul, mind, and strength (Mark 12:30, Luke 10:27).
How can we love God with our mind if it is filled with the rotten, stinking things of world? It matters. Guard your heart; guard your mind. Remember, even when no one else sees what you are thinking, God does. That is what He will judge by, not the carnal things of the outward appearance by which the world judges, but he sees inside (1 Samuel 16:7).
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