Conor McGregor is a modern man in the arena. He's fighting other men with millions of spectators watching in real time. In his instagram post he's referencing a speech by former US President Theodore Roosevelt that he gave in Paris in 1910. Very eloquently Roosevelt writes about the man in the arena. He earns respect. Critics and spectators do not.
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood." Theodore Roosevelt, April 23rd, 1910
Who are modern men in the arena?
UFC fighters. Not financial advisors.
The YouTuber putting himself out there with only 21 subscribers to his channel so far. Not the anonymous YouTube user criticizing the creator's videos.
The old lady owning a small corner shop that is closed due to the pandemic. Not the Marketing Manager sitting in his home office.
Modern men in the arena have skin in the game
The modern man in the arena has skin in modern games like investing, founding companies, starting a podcast. He is risking something, mostly his money and reputation. If I'm doing a deal with somebody who's putting in 50 % of his own money, then the both of us have skin in the game. So, both of our money and - depending on the project - also our reputation is on the line.
Only trust advice from people whose ass is on the line. A financial advisor's ass is not on the line. He's just giving out financial advice all the while selling his employer's financial products. And that's why you shouldn't trust them. "Never take advice from those who give advice for a living", Nicholas Nassim Taleb writes in his book Skin in the Game.