Most of us don't cheat for a simple reason: It makes us feel lousy. We find fulfillment in proving ourselves to ourselves. We are invigorated by genuine competition, find self-worth in meeting our goals, and, above all, know that nothing beats the feeling of accomplishment that comes with doing something fair and square.

That's why President Trump's pathological cheating in golf, alleged in a smart new book by sportswriter Rick Reilly, isn't puckish or even particularly funny. It's deeply sad.

In Commander in Cheat: How Golf Explains Trump, Reilly presents dozens of stories about how Trump has cheated at golf for as long as he's been playing. Many of them are amusing: Reilly writes about how caddies at the prestigious Winged Foot Golf Club call the president "Pelé" behind his back due to how often Trump kicks his ball back onto the fairway, and about how Trump allegedly has a golf cart rigged to go faster than anyone else's so he can race ahead to reposition his drives. Trump cheats in tournaments, cheats against pros, and cheats even when there is nothing at stake. It's almost as if Trump thinks fudging the results is part of the game.

That couldn't be further from the truth. Integrity and honor are as crucial to a great golfer's game as a solid swing. As Reilly writes, "Hale Irwin once missed the playoff at the 1983 British Open by one shot because he says he whiffed a one-inch putt on the final day. Nobody saw it but Irwin. In golf, that's enough." And Irwin isn't the exception — he's the norm. There is no greater offense in golf than cheating, in part because it's so easy to cheat in golf. There are no referees; you call your own fouls. Still, Trump's cheating on the fairway can be so elaborate and clever that even Reilly concedes he's impressed by it.

The reasons Trump cheats are mostly obvious, as are their implications. Trump longs to be the best, and can't stand coming in second. He likely sees his ability to get away with cheating as macho, even roguish, the way he has publicly boasted that finding loopholes to avoid paying taxes makes him "smart." And as Reilly points out, "If you'll cheat to win at golf, is it that much further to cheat to win an election? To turn a congressional vote? To stop an investigation?" But while I don't condone cheating on an election or to stop an investigation, that motivation at least makes sense. To cheat at your hobby is frankly pathetic.

The strangest part is that Trump is reportedly a fairly good golfer, at least according to the people who watch him play. He might not have won 18 club championships or have a 2.8-stroke handicap, as he claims, but he can hold his own without having to kick the ball all over the course. Why go to such great lengths to pointlessly lie about his abilities, then, particularly when everyone knows he's cheating? "They call him on it, but he just shrugs and cheats some more," writes Reilly. A Harvard psychiatrist blamed "a narcissistic personality disorder" for Trump's pathological cheating. "People with his disorder have no conscience about it," Dr. Lance Dodes is quoted as saying in Commander in Cheat. "He has no sense of morality about things."

More than anything else, my takeaway is not just that Trump is a cheater, but that he's the saddest sort of cheater, the kind that cheats himself. Sure, he deprives himself of "the joy, the endless challenge, golf brings" by not playing legitimately. But I think it's more than that: Trump can't stand himself if he isn't winning, to the point that he self-deludes. Why else would he continue to cheat when nothing — not money, not reputation — is at stake? As golf executive Ken Slutsky recalls in one story about a time he played with Trump in Los Angeles, "at the end [Trump] said, 'You owe me $27.' I said, 'Donald, you cheated on every single hole. I'm not paying you a dime.' He just kind of shrugged and left. He didn't seem to care."

It isn't even about pride: Trump clearly isn't bothered by his tarnished reputation in the golf world as a cheat. That's because, when you're your own referee, the only person you have to impress is yourself. Yet Trump can't bear losing. He settles, instead, for the cheapest kind of victory: The one he knows in his heart isn't real. As the anecdotes in Reilly's book suggest, he is numbed to no longer care that deep down, he knows his accomplishments are worthless, all plastic trophies and photoshopped Time magazine covers.

You can have your pick of evidence that Trump is a fairly joyless person, but nothing has quite convinced me of just how troubled a character he is like Commander in Cheat. It is one thing to cheat in business or government, and a whole other to cheat in what is supposed to be your escape from those worlds.

"Trump's [cheating is] often so over-the-top it verges on sad," Reilly writes. I have to disagree — I think it tips over the lip of the hole.