Don'tcha think one of the worst things to hear just before entering the exam hall or starting a big game or doing a major presentation, is, "Don't be nervous"?

Most likely the very first thing you'll BE is nervous!

The Mind Cannot Recognize A Negative. Saying "do not" is more likely reestablish what one isn't supposed to do than prevent it. Instead, encourage people by using the positive, e.g. "Be bold", "Be confident", "Be true", etc.

So any phrase containing an  (e.g. 'nervous', 'fail', 'scared', 'worry', etc.) is more likely to add to one's anxieties than to repudiate them.

What about words like 'sin', 'death', 'guilt', 'shame'? Can we stop using them? Nope, but I guess where sin abounds grace (should) abound even more? (smile)