If you have ever spent a lazy day, in an inner tube, drifting on the water, then you understand that drifting requires no effort. Drifting is as easy as taking a nap. This is especially true when it comes to spiritual drifting. You don't have to use oars to drift or do anything, but just sit back, relax, enjoy the moment; just follow Satan's tempting advice, "If it feels good do it."
The apostle Paul encouraged self-exam.
Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test! 2 Corinthians 13:5 (ESV)
Motivational speakers say, "You are either getting better or worse, but you never stay the same." They are right. Thus, if a Christian is not deliberately focusing on reaching higher ground, then he is drifting. He may be comfortable. He may be better than many other people in the world, but he is still drifting. Satan does not care how you drift or how far you drift, as long as you are drifting.