As one of the most prominent golf instructors of the past two decades, Sean Foley believes his failures as a swing coach still keep him up at night.

Appearing on fellow instructor Claude Harmon III’s podcast, “Off Course with Claude Harmon,” Foley revealed that he often wakes up in the middle of the night, usually around 3 a.m. He doesn’t know exactly why, but he has a good idea.

“I think it has to do with probably someone I didn’t help, and my brain understands that,” Foley told Harmon. “I don’t know, but it happens quite often actually. I do fall asleep again, but it’s there. It’s gotta be golf related.”

While Foley has had great success – his stable of current and past players includes Justin Rose, Danny Willett, Cameron Champ and Tiger Woods – he admits he hasn’t been perfect, especially when it comes to Woods. Foley worked with Woods for about four years before the pair split in August 2014. Woods, who had previously worked with coach Hank Haney, enjoyed a five-win season in 2013, but the rest of his tenure with Foley was marred by back injuries and driver struggles.

Toward the end of their partnership and after they parted ways, Foley received criticism for his coaching style, with many calling his technique too technical. Looking back now, Foley calls it over-coaching.

“At that time, I was still too methodological, and I think my original players that I met on Tour, it was perfect for all of them, and I think that what happened was I underestimated – I was too arrogant – I underestimated really the state that he was in, period,” Foley said. “[Woods] went from a deity to a punchline overnight. He won five of his last six tournaments in 2009 and came back, and by the middle of 2010, he couldn’t break par, but nothing changed – he still had the same swing, same putting, same chipping, still had Hank coaching him. So, I think that that really shows that when you go from being invincible to vincible, it’s really difficult.

“I think I over-coached him in the sense that I thought a lot of the issues were technical, more so than where they were at. But that being said, I could say that about everyone I've coached. You don't get it right all the time.”

In announcing their breakup seven years ago, Woods began his statement by saying, “I'd like to thank Sean for his help as my coach and for his friendship.” Foley maintains the two are “still very close,” and he also doesn’t dwell on what could’ve been.

“I was there for him at a time when everyone was leaving his world and I was coming into it, and I was going into Desert Storm – I mean, literally, right?” said Foley, who began working with Woods less than a year after his 2009 personal scandal. “And I knew, too, I was going to be compared to everything he had done at 22 years old. So, I kind of I understood it was going to be difficult, but I was there for him, I defended him, I loved him, I did my job as a coach, but I think it's irresponsible to think that you could do it again. I mean, everyone's a genius if they can do it again.”