It can start with just one. Maybe you've demonstrated great discipline for six months. You've exercised diligently and cleaned up your diet. Instead of feeding your appetite for junk food, you've gotten rid of the burgers and fries, the cookies and ice cream, and yes, even the Twinkies. You've experienced better health, more energy, and you're able to fit into those jeans you used to wear back in the day. Then one day you decide, "Okay, just one. Or maybe two or three, but that's all."
Six months later, those jeans are fitting tight again. You try to blow it off by assuming you must have washed them in hot water and they shrunk. But then you pull out the measuring tape and it confirms that your problem isn't hot water.
You wonder how that happened. You've continued to workout diligently. But when you begin to pay attention to your diet again you realize that you've allowed those bad habits to creep back into your daily life. What started as only one has blossomed into a daily indulgence. Instead of consuming only what you know is good, you've allowed the indulgences to creep up on you.
Regular exercise is good for you, but allowing the junk food back into your diet can negate even the most diligent workout routines. The same is true in our walk with Christ. We can be active in our church and community, diligent in our practice of daily "devotions" and one day realize that our relationship with Christ isn't what it used to be. When we take the time to examine our walk, we realize that we've allowed sinful habits to creep back into our lives. It may have started with just one small fib or just one bit of gossip. But left unchecked, sin has a way of creepin' in and growing into much more.
Getting back on track with your diet requires a conscious effort. You have to surrender what's bad and replace it with what's good. Getting back on track with your walk with Jesus requires confession and daily surrender. But if we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.