I like this approach a lot. Especially, since we know that humans tend not to notice "not" when reading and even listening. Better to say "Be brave" than to say, "Don't be afraid." A principal in a school system you are familiar with once got on the intercom and announced, as a sort of experiment, "May I have your attention, please. There is absolutely no cause for alarm." As he noted later, "Within ten minutes, there was cause for alarm."