Editor's note: We asked noted entrepreneurs to reflect on what they wish they'd known starting out and to put it in a letter to their younger selves. Paul Metselaar founded Ovation, one of the largest corporate travel management companies in the nation and a 5-time honoree on the Inc. 5000 list of fastest-growing private companies in the U.S.

Dear Paul,

As a teenager you'll have worked at your parents' travel company that put together summer tours for teenagers. One of the signs hanging in the office, which you'll never forget, is a variation of Joseph Heller's famous line: "Just because you're paranoid doesn't mean they aren't after you." To you, it's a tongue-and-cheek way of staying motivated, to always strive to do better. The true meaning of the sign won't sink in until you start law school. You'll come out of an Ivy League undergraduate program, and think you're so smart and educated that you can just coast through and ace your courses. By the time first year grades and ranks are posted, you'll have had a rude awakening as you significantly underperformed your own expectations. The good news is that that experience motivates you to study harder, and you'll began to improve.

In the future, you'll use the same principle in business, and joke about it all the time with your executive team. Despite the fact that you'll have built a successful business that has many prominent clients and does over a billion dollars in travel bookings, you'll still be weary about thinking you've "made it," because that feeling can morph into overconfidence. When that happens you'll stop pushing yourself. It's important for you to be a little bit paranoid, i.e., to assume that your competitors have people who are smarter than you are, and that they're working hard to gain on you. You'll learn that when you start thinking you're the smartest person in the room, you stop growing and cease to be innovative.

Related, the other adage that'll serve you well is Calvin Coolidge's notion that "Nothing in this world can take the place of persistence." You'll quit law to take over your father's small travel agency in 1984, and you won't have many clients or prospects. One of the biggest reasons Ovation will continue to grow is because you'll never give up. Most of your larger clients (many of whom have been with you for decades) were not won the first time you bid for their business. Sometimes not even the second. Your sales team will often understandably be disappointed when this happens, because they just look at it as a loss. You'll always say: "That's not the right way to look at it. We did not lose. We just didn't win this client yet."

Because you're an optimist by nature, whenever something bad happens, your instinct is to look on the bright side. If you don't win a bid, you'll look at why that didn't happen, where you can improve and how you can position yourself better. Your number one strategy will become persistence and perseverance. Whether it's grades or business, the lesson is to find what motivates you and to always strive to improve. There's no such thing as losing, only bumps in the road that make you stronger and help you to succeed; just keep at it after your competitors have quit or are resting on their laurels.