It curves mid-flight; hence why its named a curve ball. This is not some cliche expression. I spent my youth watching and being obsessed with the game of baseball. As a lonely kid, I spent time trying to teach myself how to throw a curve ball.
This pitch, the curve ball, spins as a result of how the ball is held and then thrown. On the receiving end is the batter, hoping to time the ball just right to hit it. The essence of a curve ball makes it hard to hit since it breaks mid-flight.
As for the cliche, yes, we will face curve balls in life. We don't have to play the game of baseball to be exposed. It is our job to hit the curve balls life throws at us out the damn park.
Its Friday and your position was just eliminated. A lump was found at your recent mammogram. The collab you did with another artist went south. The weather took a turn for the worst and so did the prognosis of someone you love. The funding never came in or the check was lost in the mail. The job you wanted went to someone else. Your boss is an asshole. The client that commissioned you for the work, backed out when you finished it. The album or book you put out did not sell. The advance you took had strings attached and you did not read the fine print...
Whatever you go through, regardless of how fast these curve balls come in: stand there, take the pitch and swing as hard as you can while making contact with the ball.