Professional investors, most of whom have underperformed the market the last 15 years, have a message for all the millennials who just started trading when their favorite company Snap went public: Investing isn't easy.

Snap shares got destroyed in the aftermath of the social network's first earnings report, likely hitting younger investors the most, according to data from Wall Street brokers.

When the parent of popular disappearing messaging app Snapchat began trading March 2, online trading broker TD Ameritrade said it gained 6,400 new clients with an average age of 38.

That's nearly a decade younger than the average age of retail clients trading Snap that day, TD said.