It's hard to land an interview, sometimes, more so than getting a job. Most companies do second interviews, and they may be harder to come by. JobMob suggests you'll have a greater chance of getting called back if you have what's called "Positive Affect".

Positive Affect (PA) is simply how much positive emotion you have and express. It is how positively you interact with others and those with PA are more enthusiastic and energetic. Research has shown that people with high PA were more likely to get called back for second interviews.

Don't have a high PA? Here's how you can boost it:
‘‘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 it's not just for job interviews but your overall life and mood. Go ahead. Try it out. There's no loss in making yourself a better person.