A 28-year-old who retired with $2.25 million shares the secret to saving

After seven years of working in the corporate world, one New York City-based twenty-something had a nest egg big enough to retire early.

She goes by the pen name J.P. Livingston on her blog The Money Habit, where she discusses how she had financial independence on the mind from an early age. When she was only 12, she picked up a copy of the personal finance classic "Rich Dad, Poor Dad," which sparked her interest in saving and investing.

When she realized she could save big by finishing college in three years, she jumped on the opportunity. Graduating a year early "really helped me financially," she tells CNBC Make It. "It saved me a year of tuition and gave me a year's worth of extra income, and between the two things, that's a $150,000 net worth swing."