In reading Joshua Harris' book, Not Even a Hint, this morning, I came across this astute quote. It was John Wesley's mom responding to her son's request for a clear description of sin.
Take this rule: whatever weakens your reason, impairs the tenderness of your conscience, obscures your sense of God, or takes off the relish of spiritual things; in short, whatever increases the strength and authority of your body over your mind, that thing is sin to you, however innocent it may be in itself.
And yes, you should read this book. It has been amazing.