It's a standard movie trope; we've seen it over and over again. The hero stands over an active bomb while the timer counts down to zero. He looks at the wires before him and asks over his phone, "Do I cut the red wire or the green wire?" His hands shake as he closes his eyes, hopes for the best, and snips the black wire.
(The hero might be colorblind)
"Fear and trembling" describe those moments as the timer beeps and the hero makes his decision. Those are also the words Paul uses to describe the daily living out of the Christian life. "Work out your own salvation with fear and trembling" (Philippians 2:12). It is an expression that means "with utter seriousness." But, of course, as Paul uses the phrase, it's less about cutting the right wire than living the life that glorifies Jesus.
(Cutting the right wire might be less stressful!)
In this message, we look at what our salvation looks like when it's lived out with fear and trembling.
(I'll give you a hint; it looks a lot like Jesus)