If you play sport, this is what you already know. One day you will lose form, fail in public, misplace confidence, tear your rotator cuff, get ignored by selectors, choke in a final and disappoint yourself. You just don't know when and which fate will befall you.
Adversity is not in the business of giving warnings and so it can show up as a concussion one afternoon or self-inflicted disgrace like Tiger Woods. Or as a more beautiful sort of challenge. Like having a baby and then doing sit-ups between nappy changes.