Kevin O'Leary says this is the best way to quit your job without burning any bridges

Americans have been quitting their jobs in record numbers in recent months, with 4.5 million workers putting in their notice in November.

And while having a conversation with your boss to tell them you've decided to quit can be stressful, it doesn't have to be, "Money Court" judge and O'Shares ETFs chairman Kevin O'Leary tells CNBC Make It.

O'Leary says his preferred method of quitting a job is hand-delivering a letter of resignation, rather than speaking off the cuff.

"I like writing a letter because it forces you to clear your mind and put forward your thoughts in the best possible manner as opposed to stumbling through it when you walk into their office saying, 'I'm leaving,'" O'Leary says.

Being thoughtful and articulate in your letter can help avoid any hard feelings and keep possibilities open for the future, O'Leary says.

"Quitting your job has a lot of interesting political issues to it," he explains. "You don't want to burn any bridges; current employers may be future employers one day and be part of your career path."

Though it is common to receive a counter offer when giving notice — particularly if you are a productive employee — O'Leary says you shouldn't consider it if you have already agreed to start another job.

"You don't want to be in a situation where you've made a decision to move and then you renege on everybody," he says. "That's horrible. You've got to have a plan and you've got to move forward."

Still, he says not to quit your job until you have another role lined up to avoid leaving a prolonged employment gap on your resume. Even if you do have a verbal offer for a job, don't put in your two weeks' notice until you've signed an employment contract with your new workplace, O'Leary says.

"Make sure you've got another job and you've signed for it," he says. "Once that's inked, then you can make your move."

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