We asked 6 big money investors about their biggest market fears - and they all had the same answer

What keeps you up at night?

It's a question you'd expect to draw a wide range of responses when posed to investors responsible for tens of billions of dollars. After all, it's not exactly like there's a shortage of anxiety-inspiring headlines floating around each day.

But as Business Insider found out through a series of interviews, there's one worry to rule them all: the Federal Reserve's reversal of the unprecedented monetary stimulus that helped drag the US out of the last financial crisis.

More colloquially described as the Fed "unwinding" its balance sheet, the mere prospect of it happening is apparently enough to strike fear in to even the most experienced money manager.

Don't believe us? See for yourself. Below is a collection of excerpts from seven interviews conducted by Business Insider, many of them by deputy executive editor Matt Turner. Each of which arrives at the same potentially horrifying conclusion.

Watch all of Turner's interviews here.