There is no such thing as a “moment of weakness”. There are however moments preceding weakness where we often ignore signs of danger and clues of imminent peril. Picture yourself, the Christian, as a train going down the tracks. The enemy wants to get you “off track” by sin. Now let’s say there is a place where the tracks end. That represents you falling into sin. A good train conductor doesn’t just stumble upon an undeveloped track. There are many signs and warnings posted along the way to help him understand what he is headed toward. If the conductor is distracted or denies these signs then when he gets within sight of the end of the tracks he won’t have time to stop a derailment due to the momentum of the train.
The way the Christian avoids situations of sin is, in some manner, the same way the conductor avoids disaster by going off track. This is to maintain a state of awareness and maturity to the direction in his life. Many of us, admittedly, wait until we are faced with obvious situations of sin to push the brakes but as we all know that doesn’t work very often. The enemy doesn’t have to convince us that sin is permissible. All he has to do is erode our strength and appetite for God so that in the moment of decision we aren’t strong enough to resist. Maturity brings situational sobriety to us Christians. The goal should not just be to stop sinning but to stop anything that could in any conceivable way lead to sin. The point is to understand when our heart is being lead away from Christ. The sooner we recognize and address this the more easily we can get back on the right track.