Think you understand compounding? What about negative compounding? : “Shark Tank” star Kevin O’Leary has some simple advice for anyone who finds investing scary: Just do it. Now. “When you’re 21 years old, or 20 or 18 or 19 and you start putting aside 10% of what you make, you’ll [have] over $1 million by the time you’re 65,” O’Leary told CNBC. He goes on to explain that impulse spending is a real obstacle for many. Unneeded clothing, pricey new wheels, morning coffee from a fancy shop — it’s all money that should be going to your future self.