Quoted by Michael Wolff in his 2018 book Fire and Fury, the email by Cohn reads as follows:

It’s worse than you can imagine. An idiot surrounded by clowns. Trump won’t read anything–not one-page memos, not the brief policy papers; nothing. He gets up halfway through meetings with world leaders because he is bored. And his staff is no better. Kushner is an entitled baby who knows nothing. Bannon is an arrogant prick who thinks he’s smarter than he is. Trump is less a person than a collection of terrible traits. No one will survive the first year but his family.

 

I hate the work, but feel I need to stay because I’m the only person there with a clue what he’s doing. The reason so few jobs have been filled is that they only accept people who pass ridiculous purity tests, even for midlevel policy-making jobs where the people will never see the light of day. I am in a constant state of shock and horror.

In Fear, the 2018 book by Bob Woodward, Cohn described two instances in which he removed documents from Trump’s desk so they wouldn’t be signed. The documents would have canceled trade agreements with South Korea and initiated a unilateral withdrawal from NAFTA.

Trump also asked Cohn to print more money in order to pay off US debt.

Cohn served as the White House’s chief economic advisor from January 2017 to April 2018, when he resigned over Trump’s decision to institute tariffs against China.

CBS News – Gary Cohn answers question about future at White House: “I’m here today”
Business Insider – Gary Cohn reportedly snatched documents off Trump’s desk to prevent him from wrecking 2 massive trade deals
The Hill – Woodward: Economic adviser ‘stole a letter off Trump’s desk’
CNBC – Gary Cohn resigns as Trump’s top economic advisor
Wikipedia – Gary Cohn