The 22-year-old from West Linton had been one of the surprise success stories for Great Britain in Moscow, breezing his way into the final at the Luzhniki Stadium when few would have expected him to.
However, the showpiece was a completely different story, with three races in four days clearly taking its toll on the Scot's stamina. O'Hare's time of 3min 46.04sec was almost 10 seconds off the winner, Kenyan Asbel Kiprop, and also almost seven behind second from last Florian Carvalho, from France.
O'Hare admitted that failing to show the world what he is really all about will live with him for some time.
"It just wasn't my day," he said. "I came into it really quite confident, thinking that if I run a good race I could come away with something that would make me happy.
"But, to be honest, if I was last in the race but still in it with 100m to go that would have been easier to take than to be that far back.
"It is hard when you are searching for those gears and they are not there. It is horrible, and it is like everyone is shouting at you to sit down and shut up because there is no point.
"All that is going through my head right now is that I have missed an opportunity to really perform and show what I have got and it is going to be another two years before I can prove myself again, hopefully.
"To learn from these races, you have to have a disappointment and all the guys who were up there have had their experience, been hammered and come back from it, and it is a British trait that you pick yourself up and fight back to where you want to be, so that is what I will do."
All is not lost for O'Hare, however, as he might not have to wait too long for a chance at redemption with the Commonwealth Games taking place in Glasgow next year.
He admits faltering in Moscow has certainly made him hungrier to prove his worth next time around.
"I was sitting on the shoulders of those in front of me and I was thinking this is exactly where I want to be," he added.
"I was thinking there were not too many people beside of me that will be pushing and shoving me, and I was stepping into the gears, which should have been smooth. But they just weren't there.
"You have those training sessions where they are not there and it is disappointing and it is just worse when it happens at a World Championships. But this will push me to work harder. There is no worse place to have a bad race."
Elsewhere on the final day, it was yet another story of heartbreak for the men's 4x100m relay as, although they did not drop the baton this time, they still ended up being disqualified.
The British quartet were celebrating winning a bronze medal but a subsequent disqualification - when it was shown that the changeover between James Ellington and Harry Aikines-Aryeetey was completed outside the changeover zone - wiped the smile off their faces.
The Canadian squad had appealed the original result and were promoted up to third, leaving Dwain Chambers, who ran a superb final 100m home straight to reflect on what might have been.
"It's emotional, to be able to cross the line in third place and secure yourself a medal is great and we were all looking forward to getting on the podium," said the 35-year-old, who has now seen the GB team fail to finish the 4x100m relay in six of the last seven major championships.
"But this is sport and it's just unfortunate that we were not able to be out there in the stadium experiencing what those guys on the podium are. All we can do now is get back home, build up our team spirits and move on to next year.
"Just because we did not succeed the way we wanted does not mean you stop, you get back up again so that's what you have to do and what we will do."
However, there was better news for the women's quartet of Dina Asher-Smith, Ashleigh Nelson, Annabell Lewis and Hayley Jones, promoted to bronze after the French team were disqualified. Britain came home in fourth place but were upgraded following a successful protest against the France team, who were second.
The International Association of Athletics Federations confirmed the French had been disqualified because their second baton exchange took place outside the changeover zone.
"I hope we get given an opportunity now, because the boys relay squad are on funding," said Lewis.
Both relays were won by Jamaica, meaning both Usain Bolt and Shelly-Ann Fraser-Pryce left Moscow with all three sprint gold medals to their names.
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