Just because a shock is a bad shock doesn't mean it should cause a recession. A recession is a monetary coordination failure. Monetary coordination failures are caused by monetary policy.
Start with a Robinson Crusoe economy. By assumption, Robinson Crusoe always allocates his resources perfectly to maximise his expected utility given his information about the constraints he faces. There are "good" shocks that raise his (expected) utility, and "bad" shocks, that lower his (expected) utility. But there are no shocks that cause a coordination failure in this economy, because Robinson Crusoe doesn't have anyone else to coordinate with. And he doesn't use money, so a "monetary coordination failure" is doubly nonsensical in a Robinson Crusoe economy.
Recessions are a bad thing, but they are not bad in the same way as a bad shock in Robinson Crusoe's economy.