Sometimes, quitting your job is the best move to make. Just ask former longtime "Law & Order" actor Sam Waterston.

Stepping away from the NBC drama, for which he worked for nearly 20 years, Waterston "felt a door opening" and newfound happiness, he said in a commencement speech at Princeton University last month. 

"For me, more and more, the things that give me joy have to do with stopping," he said.

That's despite the financial and industry security his enduring role as District Attorney Jack McCoy on the crime series brought. The part "did for me the long-haul things everyone needs from a job," Waterston said. "It kept a roof over our heads, it put our kids through college, it kept me out of trouble, it made it easier to get other work."

Filming over 400 episodes of the show was a significant mental occupation, too — that's the "astonishing" and "thrilling" realization Waterston didn't make until after throwing in the towel. "When I did finally quit, I was amazed by the amount of space the job had been taking up in my head," he said. "A big piece of myself that I didn't even know I'd rented out is mine again."

Overall, when you change your routine, "you buy space to think and shut up and to be still," Waterson said. Now he can fully appreciate springtime weather and feel the effects of regular meditation.

Quitting outside the workplace

As an Oscar-nominated actor who has won an Emmy and a Golden Globe, Waterson was in an unusually stable place in his career when he decided to leave "Law & Order."

Still, the benefits of quitting aren't limited to the workplace. Waterston urged his audience to consider disengaging from digital distractions. Being on your phone all the time can take more of a mental toll than you realize, he pointed out.

"The world isn't half as solitary as it was. You can reach anyone, anywhere, anytime," he said. "The trade-off is it's selling you stuff all day long … even selling you the idea that you're better off not having ideas of your own."

"Keeping your own head for yourself is an act of will," Waterston said. 

The adverse effects of social media on mental health have been well documented. Setting a cap on how much you use social media can, experts say, help combat sleep issues, depression and the tendency to compare yourself to others.

To improve your wellbeing, Harvard University professor Arthur Brooks recommends you adopt a "strict" time limit on social media and news consumption — not exceeding 30 minutes for either category. That doesn't mean being oblivious about world events, but involves placing more emphasis on immediate personal circumstances at home and in your mind.

"That's going to go a long way towards making a happier country," Brooks told CNBC Make It last year.

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