I did the same thing in early June. I'm sitting on cash. The only position I have is BTC, which is a gambling fraction of the portfolio.
Investing account full of cash is an itch. The reckless part of me wants to buy something, just anything. But I agree with your mentor, the stock market is insanely overvalued, and the chance of upside is immensely low.
We have to bottom out before we reach new heights. Buckle up, Tim. Good luck!