During my time as a doctor, I quickly learnt that there’s no such thing as taking a break from my profession. I got used to the idea that, even on a day off, I could be asked to give medical advice when meeting friends, be expected to help if someone faints in a mall, and even called to respond if there’s a medical emergency on the plane. Thankfully, I’ve since handed over these responsibilities to my brother.

In a way, the same holds true for us as Christians. Peter tells us that we are a royal priesthood called to proclaim God’s excellencies (1 Pet. 2:9), a mission that has been...