How to use your fear of death to live your best life, according to a psychology expert

How often do you think about death?

The thought of no longer existing is too painful and grim for many to bear and is frequently avoided, but one psychology expert thinks people need to face their fear of death head-on to live more fulfilling lives.

"My top tip is to get granular with what I call mortality math," Jodi Wellman, the founder of wellbeing platform Four Thousand Mondays told CNBC Make It in an interview. "Most people like to count their money and I like to say how about we also count our Mondays?"

Wellman, who has a Master's degree in applied positive psychology from the University of Pennsylvania, recently published the book "You Only Die Once" which is a guide to help people reawaken their passion and curiosity for life.

She explained to CNBC Make It that the average person experiences an average of 4,000 Mondays in their life, and advises people to check how many Mondays they have left every week using a calculator on her website.

This serves as a reminder of the scarcity of time, pushing people to take action in their lives.

It's based on a concept called "temporal scarcity," meaning we value assets that are temporary more than the ones that are infinite, according to Wellman.

"So we have to get really in tune with the temporary nature of our lives ... because otherwise, we won't take action, we will languish," she warned.

Most people settle into unfulfilling jobs and put off passions like going to that tennis lesson or learning Italian, but "later is an elusive time that may never come," Wellman said. When you remember how many days you have left, you're more likely to book that tennis lesson.

"If you were going to die tonight what would you wish you had taken action on? Maybe there's an opportunity to start that