As the richest man in the world, Bill Gates is no stranger to success.

So when the billionaire tech mogul and philanthropist offers insight or advice, it's smart to listen.

Last Monday, the Microsoft founder and co-chair of The Bill And Melinda Gates Foundation hosted an "AMA," or "ask me anything," session on Reddit, during which a participant inquired, "If you could give 19-year-old Bill Gates some advice, what would it be?"

Here's what Gates had to say:

"I would explain that smartness is not single dimensional and not quite as important as I thought it was back then. I would say you might explore the developing world before you get into your forties. I wasn't very good socially back then, but I am not sure there is advice that would fix that — maybe I had to be awkward and just grow up..."

In short: Intelligence isn't one-dimensional — and it's not the only ingredient required for success.

This isn't the only time Gates has doled out advice for navigating your years as a young adult. One of his best nuggets of wisdom comes from fellow billionaire and friend, Warren Buffett: Keep things simple.

In a 2009 interview with CNBC, Gates said:

"You look at his calendar, it's pretty simple. He picks the things that he's got a model of, a model that really is predictive and that's going to continue to work over a long-term period. And so his ability to boil things down, to just work on the things that really count, to think through the basics — it's so amazing that he can do that."