"I think most of the struggles that I've had over here, aside from injury, is just the change of environment. I haven't been completely comfortable. I guess it's something I'm going to have to get used to."
"I haven't felt settled. Every time I hear something snap or go bang I think someone is lighting up. It's a difficult one to explain, I'm not complaining, but I know that I haven't felt relaxed in my surroundings."
The Tauranga native believes he didn't create the right environment needed to succeed in his first major meet, but knows what needs to be done.
"When I go over to Australia it's really fun and I step up with better times on the track. So I need to create the same sort of situation and circumstances elsewhere in the world."
Millar leaves London ranked as the 33rd quickest sprinter in the world over 100 metres and the 39th over 200.
Heading into the World Champs, he was 53rd in the 100 and 33rd in the 200.
"Although I was disappointed I didn't go faster in the 100, last night sort of looking back at the difference between that time and my personal best, compared to a lot of the other athletes and their personal bests, I was a lot closer than most people were to being in top shape."
"It was a lot of fun, a great experience and it just gives me a lot of passion and a lot of fire to get back out there and start training. I want to get to the standard that some of these guys are at and start taking some scalps from the Commonwealth Games onwards."
Like other members in the Athletics New Zealand team, Millar heads to Taipei in the next couple of days to compete at the World University Games.
The 24-year-old is looking forward to competing in an environment more familiar.
As Millar slowly starts to make his way away from the Olympic Stadium track and the media mixed zone, he offers thanks to those that have supported him to get to London and also reminds those that doubted he could be here.
"You know it's really good after all the years of people telling me not to do sprints, you'll never make it to a World Champs, do 400 metres if you want to sprint, but if you want to be realistic move up to the 800... To finally have heard the last of them and now hear cheers of support instead, it's an amazing feeling to have gone through it all and turn around and see that you're being pushed forward instead of back".
Charlie Bristow is in London thanks to Air New Zealand.
