Self-made millionaire Grant Cardone believes in .
"There are 168 hours in a week. You should be working most of them," says the entrepreneur, who himself puts in about 95 hours a week.
If you want massive success, you have to grind — and you have to be prepared to do it when no one else is, recently. Instead of doing what the crowds do, "work when others aren't."
That means working weekends and holidays. Use Valentine's Day, Columbus Day and other conventional days off to focus on earning and get ahead, he says: "Spend your time working holidays when no one else is."
Ultimately, "if you want to change your condition, you have to work," Cardone added. "If you can outwork the rest of the population, you're going to get lucky."
"Shark Tank" star Daymond John, who while , has a similar mentality. Ultimately, the secret to success boils down to one thing, John argued: "Work. Bust your butt. Get up before everybody, go to sleep after everybody, and bust your butt. That's it."
Not everyone agrees with this approach. "More work is never the real answer," said billionaire LinkedIn co-founder Reid Hoffman on "The Tim Ferriss Show " podcast. "The sort of grit you need to scale a business is less reliant on brute force. It's actually one part determination, one part ingenuity and one part laziness. Yes, laziness."
"You want to minimize friction and find the most effective, most efficient way forward," Hoffman continues. "You might actually have more grit if you treat your energy as a precious commodity."
But for Cardone, long hours are the answer: "If you gave me $5 billion, I'd still be grinding tomorrow."
Like this story? Like CNBC Make It on Facebook.