Imagine the scanario:
You successfully complete your first course in freediving, you loved the experience and can't wait for your next chance to dive down to 20m. Six months later, on your next holiday, you excitedly sign up for a freediving excursion to eplore the local reef, but it all seems harder this time, you are less relaxed, the breath hold is shorter, you forget how that whole equalisation thing works again....
Or
You are an Advanced Freediver, 'did the course got the card!'. You are more confident with your technique, happier holding your breath but you are turning at the same depth on every...single...dive and can't figure out how to get past this invisible obsticle that is holding you back......