Fool in the shower
"Fool in the shower" is an analogy attributed to late free market economist Milton Friedman. It refers to a bather who, thinking his shower water is too cold, turns the hot water all the way up and scalds himself in the process.
It's better to make small, incremental moves than big jumps so that you don't get burned.
Friedman was using the analogy to caution central bankers against moving too fast with any monetary policy and the term got a lot of play in the winter of 2008 when Fed Chairman Ben Bernanke cut the federal funds target rate some 225 basis points in just four months leading many to wonder whether Bernanke was "the fool in the shower."