A friend of mine spends 20 to 30 minutes a day solving Sudoku puzzles. He says it improves his speed of mental processing and makes him, well, smarter. Hold that thought.
Ask people which factor contributes the most to success and most will choose intelligence, even though science says you also have to be lucky: Right place, right time. Right person, right time. Right idea, right market, right audience at the right time.