Think of the last genuinely good thing that happened to you. Almost certainly you didn't see it coming and couldn't have written it into a diary. Good news mostly arrives sideways — a message from someone you'd stopped expecting to hear from, a door that opened because of a conversation you'd forgotten having.
Fear, meanwhile, is a confident forecaster. It produces vivid, detailed versions of next month and delivers them without hedging, and it has been wrong far more often than it will ever admit.
You don't know what's coming. That cuts both ways, and one of those ways is in your favour.