Hedge fund manager Whitney Tilson, the founder of Kase Capital, gave some sage life advice to nearly a hundred graduating 9th grade boys during a commencement speech on Friday.

Speaking at his alma mater, Eaglebrook School, a private 6th to 9th grade boarding school in Deerfield, Massachusetts, Tilson told the boys: “If you are a dumba--, there will be consequences!”

This is Tilson's so-called “No. 1 Immutable Law of the Universe” that he's been telling his three teenage daughters for years.

Throughout his career, Tilson has made many public presentations and television appearances. This, however, was his first time speaking to an audience of teenagers. He wanted to give the 15-year-old boys a "memorable" speech.

“I like it because it’s memorable: I’m pretty sure that the word dumba-- has never been used in any commencement address ever. The question is, is it meaningful? I think it is.”

He continued: “[The] foundation for a a successful life is playing defense. And by that I mean avoiding the obvious mistakes that can really set you back. I’m not talking about the big, general things: if you’re mean to people, don’t expect to have many friends; if you’re lazy and dishonest, you won’t have much of a career; if you don’t take care of your body, of course it’s going to break down…. No, I’m talking about the blindingly obvious things, ranging from touching a stove to see if it’s hot (I did that once) or touching an electric fence to see if it’s live (I did that too), all the way up to things that can derail – or end – a life.”

Tilson cautioned the boys that the "biggie" that can derail their lives is binge drinking alcohol, especially in college.

"I'm not saying you should be a teetotaler -- go ahead, have a drink or two...maybe even three. But be really careful about getting totally smashed because there are so many permanently bad things that can happen," Tilson said.

He added: "By now you’re probably thinking, 'Jeez, what kind of commencement speaker is this? What a downer he is! When is he going to tell us how great we are, how we should put on our sunglasses because our future is so bright, and how we need to seize the day?' Well, you are and you should – but the reason I started with these stories is because the foundation for a successful life is playing good defense. If you want to get ahead, you have to start by not falling behind," Tilson said.

In addition the "don’t be a dumba--" advice, Tilson encouraged the boys to form good habits, quoting famed investor Warren Buffett: "You can transform yourself into the person you want to be, but you have to decide early because the chain of habits are too light to be felt until they are too heavy to be broken."

Tilson continued: "All the little things you do dozens of times every day – your habits – define who you are – and once these patterns are set, they’re really tough to change. So if you remember anything from today, I hope it will be this: it’s critically important to develop good habits early in life."

The two habits he really encouraged were: "work hard, be nice," which is the slogan of KIPP charter schools, which Tilson has been heavily involved in for years.

"It’s so simple that you might dismiss it, but if you think about it, those four words capture an awful lot of what you need to be successful in life."

According to Tilson, "work hard" is not just about immersing yourself in your education and putting in a lot of hours, but it's also about having "grit, determination and resilience."

"All of us face setbacks in life -- it's how we handle them that's critical. One study measured students' IQ and also grit -- and it turns out that grit was twice as important in determining life outcomes," Tilson said.

As for being nice, that's another way of "not being a jerk." He encouraged the boys to be grateful and to find ways to be a "giving person."

"I’ve thrown a lot at you here, so let me quickly summarize: defense wins championships, work hard, and be nice. If you do these things, I promise you that you’ll lead a long and rewarding life, filled with love, laughter and happiness. It’s yours for the taking."

Julia La Roche is a finance reporter at Yahoo Finance.

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