Editor’s Note (December 21, 2017): Through to the end of the year, BBC Capital is bringing back some of your favourite stories from 2017.

Are you putting off a big project that you really should start today – perhaps holding out for the perfect possible time?

You could be on to something.

Most people decide to make changes in their lives around landmark dates. Mondays and the New Year are obvious choices for initiating a new, goal-oriented behaviour, such as getting started training for a marathon, getting out of debt or striving for a promotion.

Experts suggest people are more likely to feel motivated if they launch goals at a time that is personally meaningful to them

Academics call these dates ‘temporal landmarks’ – important points on the calendar which mark the passage of time and help people organise their lives into ‘chunks’.

But experts suggest people are more likely to feel motivated if they launch goals at a time that is personally meaningful to them.

Hengchen Dai, assistant professor of organisational behaviour at the UCLA Anderson School of Management, is one of several researchers who have studied this phenomenon, called the ‘fresh start effect’.

You may also like:

- A unique way to get work done
- Manage your focus, not your time
- A novel trick to beat procrastination

Dai says that whatever you feel is a “psychologically significant transition point,” where you can leave behind your past, imperfect self – and your failures – is a time you’ll feel more motivated. “If it has a personal meaning or personal relevance to you, you are more likely to take on some activities to pursue your goals.”

While this might be a weekly, quarterly, or seasonal cycle, you don’t need to stick rigidly to the calendar. In fact, you might have more success in getting started if you pick a different date – perhaps when starting a new job or the start of a new semester.

A significant amount of people take on new challenges on birthdays ending in nine. So, you’re more are likely to, say, sign up for a marathon aged 29 or 39 than at 30 or 40

Birthdays are also a popular choice, particularly if you’re approaching a milestone age. One paper by professors at New York University and UCLA found people are more self-reflective and make big life decisions as they approach a new decade.

In fact, the study found a significant amount of people take on new challenges on birthdays ending in nine. So, you’re more are likely to, say, sign up for a marathon aged 29 or 39 than at 30 or 40.

Break points

New York-based career coach Rebecca Kiki Weingarten says her clients are always looking for fresh starts, but the timing “depends on each person's work style and motivational needs. Some clients plan for after vacations, [while] some are athletes and use their specific sport season and work around that.”

Some people find that being laid off, or a relationship breaking-up is the best time to take on projects, careers, financial changes, or personal changes that they'd been putting off for a long time or ‘never got around to’,” says Weingarten.

Some of her clients are more motivated in the lead up to a significant birthday, an anniversary commemorating the birth or death of a loved one.

Success not guaranteed

People tend to have more long-term success with goals that require a one-off action, such as signing up for retirement savings.

But while we might be able to harness a meaningful date for a fresh start, this is no guarantee of success in the long run, says Katherine Milkman, a professor of behavioural economics at The Wharton School at the University of Pennsylvania, and co-author of the study into the fresh start effect with Dai.

Dai agrees. “In terms of how long-lasting that behaviour will be and whether the persistence will vary based on temporal landmarks, that’s an open question we’re still exploring.”

To comment on this story or anything else you have seen on BBC Capital, please head over to our Facebook page or message us on Twitter.

If you liked this story, sign up for the weekly bbc.com features newsletter called "If You Only Read 6 Things This Week". A handpicked selection of stories from BBC Future, Culture, Capital and Travel, delivered to your inbox every Friday.