Jack Abraham, 25, is a successful entrepreneur. In 2008, he left Wharton to found Milo.com, a shopping engine that searches local store shelves in real time to find the best prices and availability for products of all kinds. In December 2010, eBay bought Milo.com for a reported $75 million. Abraham spoke with Knowledge@Wharton High school from his office in San Jose, Calif., about the triumphs and challenges of entrepreneurship -- starting with his days at Langley High School in McLean, Va. -- and what it takes to succeed.…