The 17-year-old from Whitehorse was the Yukon's flag bearer at the opening ceremony of the Canada Summer Games, where he played tennis in the first week of the multi-sport event and will compete in athletics next week.
As hard as it is training for two sports, while going to school and working, it's an empty hour that really frustrates Halliday.
"Because I'd immersed myself in the running and the tennis so much, when I wasn't doing them and I was offered free time I was so unsure of what to do with it I was almost paralysed," said Halliday on Thursday. "The hardest part about training that much, for me, was the part where I wasn't training, which is kind of weird to say.
"It's a weird feeling, but I mean, I did it so much that when I was off I didn't know what to do with myself."
It's surprising that Halliday finds his free time so difficult since the rest of his schedule would be a burden for most people.
He attends St. George's School in Vancouver during the fall and winter, then returns home to Whitehorse in the summer where he works as a day camp counsellor. When he's not in school or at camp, he's training for the 3,000-metre steeplechase and other long-distance events. He then works his tennis training program around the rest of his schedule.
Practising in Vancouver isn't particularly arduous, but Halliday finds exercising in the North during the winter the most difficult part of the training regime itself.
"The Yukon doesn't have any indoor tennis courts, so there's this gym that we train on and that's really brutal. It's a rubberized floor, it's not even tennis surfaces," said Halliday. "That's where the kids have to go in the winter and it's just awful.
"I guess that's just one of the perks of living in one of the big provinces: facilities. We either don't have the money or we don't have the population to support a full-fledged tennis facility. We just have to try and do what we can."
Long-distance running during a Whitehorse winter isn't any easier than tennis in a rubberized gym.
"We do it on snowshoes in the winter, that's how we compensate," said Halliday. "It's a real workout."
Halliday allows that there are some advantages to such difficult training conditions. The rubberized indoor tennis courts have helped him develop better reflexes and the snowshoeing has made his legs stronger. But there are more cons than pros.
"The thing is, with the timing of your stroke, if the ball's always skidding on the ground like that and going super fast you're going to develop a lower stroke and you're not going to be able to deal with the spins as much because they won't be as effective on the rubber," said Halliday. "As soon as you get into the real surfaces the spins are going to come into play, the balls are going to bounce high so you're swing's going to be compromised.
"There's a couple of advantages, but the disadvantages outweigh them a lot."
Snowshoeing presents a different set of challenges for Halliday and others running in the Yukon.
"You don't go as fast so you don't get used to speed, it's hard to sprint on snowshoes," said Halliday. "Second of all, in running, you're kicking your legs up a lot higher but the snowshoes aren't attached at the heel, so if you kick your legs up higher your snowshoes are going to fall off. You have to shuffle a little more.
"It just develops a different kind of stride that you have to fix every spring. It's pretty annoying."
Still, Halliday is proud to represent the Yukon at the Canada Summer Games and volunteered to play tennis for the territory — adding a week to his stay in Sherbrooke, Que. — because he saw it as an opportunity to mentor the younger athletes in his delegation.
"I thought 'I'm going to be one of the older guys, I'm going to try be a role model for the younger kids. If I don't go, it's going to be really hard for a lot of them,'" said Halliday. "So I decided it'd be a good thing for the team, even if I have to focus on more things, it'd be a good thing for the team if I ended up going."
Most of the time Halliday leads by example, but he also tries to do little things to support the younger members of the Yukon's delegation.
"It's as easy as just sitting by their court and cheering for them when they get a point," said Halliday. "Playing against these bigger provinces sometimes it's hard to keep yourself motivated. They're super strong, right? So just sitting behind them, giving them a couple claps, a couple cheers, that always helps."