"But if your eyes are bad, your whole body will be fill of darkness. If then the light within you is darkness, how great is that darkness! (Matthew 6:23)"
Freedom. Isn't that such a wondering thing? Especially in the land of the free, America, where we have the freedom of speech, of religion--well, you name it, we've got it. But as Christians, we have come to know that although God allowed the freewill to choose in our lives, true freedom comes with laws.
God told Adam to "be fruitful" in Genesis 1. However, in Genesis 2, God gave Adam The Commandment, telling him not to eat from the tree in the middle of the Garden of Eden. God did give freewill. But God also did give laws. He gave a law that asked Adam to do something and gave him a law telling him not to do something. There are some who may misunderstand this picture completely and irrationally conclude that God did not give man freewill but only controls man. This theory can never be true because God creates man to be partners of love with him. When man becomes fruitful by maturing through the love of God, he has the capacity to not only give joy to others by sharing the love but also feel joy himself through that same flow of love. God gave man freewill so that man could fulfill a relationship of true love with God by choosing to love God back without any hint of force.
There is freewill but there are still things we shouldn't do. For example, let's speak of the eyes. There are so many filthy scenes and images to look at nowadays as digital technology further distributes these spectacles to massive internet users at an alarming rate. There goes the proverb, "The eyes are the windows to the heart." Anything that we see with our physical eyes can impact our spiritual heart, defile it even. We know that from the heart comes our actions, at times, actions of sin.
A simple approach can be taken in order to avoid sin, actually. Considering what enters the eyes as the starting point to sin, as defiled images taint the desires of the heart and therefore causing man to sin, avoiding sin is quite easy--don't look at impure things. Why not cut sin off from the root?
We can admit that to avoid looking at every possible impure image on the internet, highway billboards, at times people will prove to be a seemingly impossible feat. However, when there's a will, there's a way. Training ourselves will be difficult, but the motive to begin to train must come from an understanding of why God has given us laws against those things. It's only to protect us.
Instead of only focusing on the sin committed through the execution of a physical action, Jesus focused on the sin of the heart. Lust is one of them.
"But I tell you that anyone who looks at a woman lustfully has already commited adultery with her in his heart. (Matthew 5:28)"
It's invisible. However, it can still be a sin. Lust enters the body casting darkness within, attacking the strongest fort of the person: the heart. Now, if the center of the person gets knocked out, it's all downhill from there. God knows this. He gave us laws so even though we have the freewill to walk across the street whenever we choose, possibly getting run down to a pancake, God will give us the red light as an indication that it's not safe.
Well, the best advice to avoid sin would be obedience. Sometimes, it may feel so frustrating to listen to and obey God. But that's just the only way.