Be self-controlled and alert. Your enemy the devil prowls around like a roaring lion looking for someone to devour. 1Peter 5:8
I remember what it feels like to be stalked by a dangerous predator. During my time in the jungles of Vietnam we came across tiger tracks more than once, and had to deal with the fearful thought that we may have been followed by such a beast. We hadn't been trained in hand-to-claw combat, so we weren't sure how we would react if attacked by a tiger. I certainly didn't want to find out.
In the mountainous jungles that my rifle platoon patrolled, we practiced constant vigilance. One could not relax in such an environment, realizing that not only were there enemy soldiers in the area, but all sorts of other creatures such as snakes, leeches, and the aforementioned tigers.
Followers of Christ need to understand that the world in which we live is also a hostile environment. I was reminded of this last Sunday in my pastor's sermon. We have a predator who follows us, seeking in every way he can to destroy us. His mission is to "kill, steal, and destroy," (John 10:10). The good news is that we have the spiritual weapons to do battle with this predator, Satan. These weapons are prayer and Scripture. In addition, we have the full armor of God (Ephesians 6:11) at our disposal. But if we fail to be vigilant, we leave ourselves vulnerable to being harmed by this predator, the devil, who constantly seeks to take us down.