The Apostle Paul states, "For what I am doing, I do not understand; for I am not practicing what I would like to do, but I am doing the very thing I hate." (Rom 7:15). Have you ever made up your mind that you are going to do something yet found yourself doing the exact opposite? For example: many people make up their mind to join a gym and get in shape around January. Come March the only thing they are exercising is their wallet to pay a membership they no longer use. Or maybe you had a habit that you wanted to stop (ex: smoking). One day you made up your mind to quit but find yourself sneaking a smoke here and there. Even though this is in the Bible we find that the sentiment is expressed by people like Johnny Cash and experience by all of us in our daily lives. You do not need the Bible to realize that at times you are at war between your "general will" and your "immediate desires".
Why is it that we can "generally" make a decision but find that in the "immediate" situation we cannot live up to our wills? The Bible says it is because we have a sinful nature. That is, our natural inclination is to practice evil. Self-control is a discipline while you don't have to try to let yourself go. This is something which can be used in evangelism or even apologetics. It is a universal experience of mankind that we fight between our general wills and immediate desires. Now if we are just molecules in motion, as the new athesists want us to believe, then we shouldn't have conflicting wills. Whatever chemical reaction happens will cause us to do a certain action. Atheism cannot explain how I can seemingly decide to do something and yet allow my desires to take me to the contrary. An even stronger proof is that atheism cannot explain how I can have immediate desires to do something then make the decision to suppress those desires and do the opposite. For example, when someone makes me angry my immediate chemical reaction is to get angry and inflict physical violence upon them. My general will tells me to obey the law of the land and love my enemy. Christianity has an answer for this while atheism fails. Are we just molecules in motion with no real "free will" or do we have the ability to make decisions that overcome the chemical reactions in our brains? The Bible affirms the latter.