To live a life of victory in the Christian walk it needs constant watchfulness. This is because we have a powerful enemy who is constantly on the prowl. So in 1 Peter chapter 5 and verse 8 we are warned to be self-controlled and alert. This is because the enemy who is the devil prowls around like a roaring lion looking to devour someone.
Well, the devil may not attack us the way we expect. This is the reason why constant watchfulness and alertness is required from our side. It is a common experience among Christians who desire a walk of victory to fall into sin in ways they least expected. This happens because they keep watching in the area they are more often tempted. Then they feel safe like a king who has kept guards in all the entrance points of his palace. But this kind of false-security is dangerous. That is why in 1 Cor. chapter 10 verse 12 Paul warns us to be careful not to fall if we think we are standing firm.
We have a lesson to learn from the Israelite history in this regard. When they were camped in the desert Balak king of Moab hired Balaam to put a curse on the Israelites. But because God loved Israel He prevented Balaam from cursing and turned the curse into a blessing. Though the Israelites were saved in this manner they were attacked in another manner. They were induced by Moabite women into sexual immorality thus bringing a plague on the Israelites. Many thousands died. But the cause was Balaam who had advised the women to tempt the Israelites. The source through which ruin came was the same. Only the method differed!
(Ref. Numbers 22 to 25, 31:15,16 & Deut. 23:5)