I did a message entitled Angels and Demons The Truth on Sunday, November 8, 2009 that you can view www.mercychurchKC.com/media or look for it on our iTunes account under "Mercy Church KC". I did the message because of the popularity of the low budget movie, Paranormal Activity.
I always talk to my Jana (my wife) after my talks to see what she thought about my delivery, content and what I could improve and she said I should have (or could have) better clarified my statement that "we open ourselves up to the devil by sinning." I agree, so here is my clarification on that statement.
I believe that statement to be true NOT in the sense that if I sin, the devil can or will come in and make my car break down or something like that... what I mean by that statement is that when we open ourselves up to sin we open ourselves up to feel more comfortable with continuing to sin, for example: If I (as a married man) allow myself to think (or dwell on) about other women in an improper way, that could lead me to looking at porn, which then leads me to look at more porn, then this could lead me to improper interactions with women, then ultimately lead me to having an affair. There is no married person on planet earth who has ever had an affair without FIRST thinking about it! You don't trip over a shoe and fall into bed with someone! Hello!
So, all that said... THAT is what I was saying when I said that when we chose to sin when are opening ourselves up to further sin and being comfortable with making bad choices. I believe we become hardened towards God when we RESIST GOD and His leading in our life.
Side Note: Every human (that would be me and you) have a good side and a bad side ... we must FEED THE GOOD side in us and the best way to do that is to follow God's will for your life. Doing good is addictive ... the closer you draw to God, the closer He draws to you.