One of Paul's prophecies foretells of a falling away shortly before Christ's return. The coming apostasy is worldwide in scope and will put pressure on all.
In a secular sense, apostasy is abandoning one's political party, principles, or cause. Biblically, apostasy is rebellion against God or the abandonment of faith.
What we believe automatically determines what we do; it is impossible to separate faith and works. If Jesus is not our source of belief, our works will suffer.