Subjects in an experiment were instructed to spend time visualizing and writing about their best possible future selves.

Here’s what they were told:

“You have been randomly assigned to think about your best possible self now, and during the next few weeks. ”Think about your best possible self” means that you imagine yourself in the future, after everything has gone as well as it possibly could. You have worked hard and succeeded at accomplishing all of your life goals. Think of this as the realization of your life dreams, and of your own best potentials. In all of these cases you are identifying the best possible way that things might turn out in your life, in order to help guide your decisions now. You may not have thought about yourself in this way before, but research suggests that doing so can have a strong positive effect on your mood and life satisfaction. So, we’d like to ask you to continue thinking in this way over the next few weeks, following up on the initial writing that you’re about to do.”

After four weeks, they were found to have more positive emotions than control subjects.

Reference: Sheldon, Kennon M. and Lyubomirsky, Sonja. (2006). “How to increase and sustain positive emotion: The effects of expressing gratitude and visualizing best possible selves,” The Journal of Positive Psychology, April; 1(2): 73-82