1) Write down your worriesResearch shows writing about your worries can calm you and even increase performance:

…for students given the opportunity to write before the exam, those highest in test anxiety performed just as well as their less anxious classmates. “Writing about your worries for 10 minutes before an upcoming exam leveled the playing field such that those students who usually get most anxious during exams were able to overcome their fears and perform up to their potential,” Beilock said.

Projects at work bothering you long after you leave the office? Write down a plan for how to deal with them before you leave.

2) Write down the good things that happenProfessor Martin Seligman at the University of Pennsylvania, who developed the technique, refers to it as 3 blessings.

A big part of staying positive is perspective. This technique has been proven again and again to help people improve their outlook.

Seligman explains it in his book Flourish: A Visionary New Understanding of Happiness and Well-being:

Every night for the next week, set aside ten minutes before you go to sleep. Write down three things that went well today and why they went well. You may use a journal or your computer to write about the events, but it is important that you have a physical record of what you wrote. The three things need not be earthshaking in importance (“ My husband picked up my favorite ice cream for dessert on the way home from work today”), but they can be important (“ My sister just gave birth to a healthy baby boy”).

Next to each positive event, answer the question “Why did this happen?”

More here.

3) Write down the things you’re looking forward toPeople who devote time to anticipating fun experiences are happier.

In fact, often the anticipation period ends up being more pleasurable than the event itself:

Research shows that people can reap substantial enjoyment from anticipating an upcoming event even if the event itself is not entirely enjoyable. Examining three different vacations ranging from a trip to Europe to a bicycle trip through California, Mitchell et al (1997) found that people viewed the vacation in a more positive light before the experience than during the experience, suggesting that anticipation may sometimes provide more pleasure than consumption simply because it is unsullied by reality. Not surprisingly, then, people who devote time to anticipating enjoyable experiences report being happier in general (Bryant, 2003).

So make plans, write them down and when you need a boost to keep staying positive, look at the calendar.

From Shawn Achor’s The Happiness Advantage:

One study found that people who just thought about watching their favorite movie actually raised their endorphin levels by 27 percent. Often, the most enjoyable part of an activity is the anticipation. If you can’t take the time for a vacation right now, or even a night out with friends, put something on the calendar—even if it’s a month or a year down the road. Then whenever you need a boost of happiness, remind yourself about it.

I'm unclear on whether TYPING (on a computer) constitutes WRITING (which often involves a pen).

Medium says we should not write alone: https://medium.com/about/8304190661d4

Key quotation:

Whether it’s getting a friend to help you recall a story, asking a colleague to help you construct an argument, or just finding a second set of eyes to catch typos, on Medium, you can share the best version of your stories and ideas — and start creating better things _together_."

Unstated in Eric's article is that the key to writing is to do it every day.

It does not have to be much:

Just jotting a few words down can make a big difference in your mood and perspective.

The important thing is to do it every day.