Genesis 4:7b …sin is crouching at your door; it desires to have you, but you must master it.
Sounding like a classic kung fu challenge or a line from Star Wars, God warns Cain to be on the alert for sin and to learn to control it, rather than be controlled by it.
Reading further, Cain did not master it but instead, was overcome by it, and killed his brother. Part of the skill of mastering sin is learning to recognise it crouching, hiding, sneaking up and lying in wait. It always looks smaller and less powerful than it is. It can appear cute and even fluffy but this crouching tiger, hidden dragon gets big and nasty and ugly very quickly, as soon as we let it in the door. Once the door is open and let in, it is very hard to get rid if it. Even harder when we entertain it, feed it and encourage it.
CamisGWare 