The latest obsession on TikTok is the "Winter Arc" challenge, which sees young people get ahead of their New Year's Resolutions.

Winter Arc TikTok is flooded with videos of young men and women wearing dark-colored oversized hoodies and athleisure, working out in the gym, or going for early-morning runs.

"These are the months where a lot of people tend to slow down … this is the time where people tend to let their foot off the gas," says one TikToker, Carly Upgraded, in a video with 4.6 million views.

Carly says the Winter Arc is all about being "laser-focused" on your goals, so that you're transformed by the new year. Her goals include waking up at 5:30 a.m., having a workout and meal plan, reading books, and even posting more content on TikTok.

Despite its recent popularity, the now-viral trend has actually been around as a concept for years, according to celebrity fitness trainer Michael Baah. Baah has worked with high-profile clients including British soccer legend Gary Lineker, boxer Ezra Taylor and Strictly Come Dancing star Tasha Ghouri.

"Whether it's fitness, financial, whatever remit you're in, you can create a challenge during the last 90 days of the year — the last quarter of the year — to get you ready and set for the next year ahead," Baah told CNBC Make It.

He said it takes 66 days to form a habit, so the Winter Arc helps ease the process of transitioning into your New Year goals.

"The best time to plant the tree was 10 years ago. So starting your challenge early is going to keep you locked in and help you get into your routine a lot quicker than starting on the first of January, when you're battling all of those demons, and the chocolate and Christmas leftovers in the fridge," he said.

However, there does appear to be a dark side to the trend, with some TikTokers taking things to the extreme, saying they'll cut off all romantic relationships, have no form of human contact, and go to the gym six days a week during their Winter Arc.

London-based celebrity therapist Malminder Gill warned against this approach, saying these extreme goals are a form of "self-harm."

"You're challenging yourself to actually speed up depression," she told CNBC Make It. "We need social interaction, we need balance, we need sunlight."

Here are four expert tips to create healthy, realistic Winter Arc goals:

Improve by 10%

Although Winter Arc extremists might have you believe you need to go from zero to 100, this will lead to burnout, according to Gill.

Her philosophy is to take whatever you're doing currently — such as in your diet, fitness regime or social life — and figure out how to improve it by just 10%.

"This is better because it's easier to maintain and there's less likely to be this cliff drop," Gill explained.

It can be as simple as choosing not to add any sweetener to your coffee, or adding an extra 10 minutes to your gym workout, Gill advises.

Fitness coach Baah, meanwhile, encouraged "consistency over intensity" to help get you to the finish line.

"I always say to people: start where you are. If you're not a gym person, don't start becoming a gym girl from day two and start smashing seven days in the gym, because that's not going to be consistent," he said.

"Instead, incorporate 15-to-40 minute workouts in the gym semi-regularly, rather than two-to-three-hour sessions every day, so that after a long a day at work you're not put off and lose motivation."

Complete an internal check

Preparing your goals also requires you to assess your emotions and feelings throughout the year.

"Decide 'what is it that brings me energy?'" says Katia Vlachos, certified coach and meditation teacher. "What is it that recharges me, that energizes me, that brings me joy? And what is it that depletes me?"

Gill described this as an "internal check," which requires people to get real about their feelings. "One of the absolute best self-care things you can do is checking in with yourself. What do I think before the world tells me what I should think?" Gill said.

This could mean cutting out activities that drained you this year, setting boundaries, and doubling down on habits that are helping you grow.

'Well-formed goals'

As people approach the end of the year, many look back on a list of vague goals that never came to fruition, Gill said, which can cause feelings of guilt and shame.

"When it comes to guilt in this context, specifically this year, you're just going to have to suck it up, because next year, you have to define your goals and outcomes much better," she added, noting that more manageable targets are less likely to lead to these feelings.

"If you're feeling guilt or regret because of your goals that have been unachieved or not accomplished, it's because they weren't well-formed goals or well-formed outcomes," she said. "You didn't create the goal in a way that fits in with your life. You didn't do the full, forward-thinking. You didn't think of all of the traps that might be waiting for you."

Life coach Vlachos emphasized the importance of creating flexible goals that align with your values, as opposed to strict, measurable goals. That way you can adapt your goals as you grow through the year.

"Our goals should not be our cages," she said. "They should motivate us and pull us forward and help us grow, not keep us limited or lead us to burn out."

Don't forget to 'nourish your soul'

A lot of Winter Arc goals outlined on TikTok are focused on the physical and aesthetic, but ignore the mind and soul.

"Do you nourish your soul? Do you do the things that bring you joy and make you happy? I find that as important as the physical stuff," Vlachos said.

She stressed that it can be more challenging to address big questions about your feelings and emotions rather than going to the gym.

One way to get in tune with your feelings can be through meditation, and it doesn't take up a lot of time, Vlachos said. Her favorite meditation exercise, for instance, is called "16 seconds."

"You basically breathe in for a count of four. You hold for a count of four. You breathe out for four, and then you hold for a count of four," she said.