Merriam-Webster defines pessimism as “an inclination to emphasize adverse aspects, conditions, and possibilities or to expect the worst possible outcome.” We all have our moments when we view our glasses as half-empty, but when people are plagued by pessimism, frankly, they’re no fun to be around.

Often, people become pessimistic when they are under stress. Losing a loved one or a job, or experiencing a crisis such as a fire, an accident, or an illness can color your outlook with gloom.

But pessimism harms you:

• By stealing your joy when something good happens, because you anticipate everything that could go wrong (yes, she agreed to go out with me, but when she finds out I earn minimum wage, she’ll dump me for someone richer)
• By preventing you from making positive changes in your life, because you fear you’ll fail (I could apply for a promotion, but if I don’t get it, everyone will think I’m a loser)
• By highlighting other people’s worst qualities, which will destroy your trust
• By giving you a negative attitude about life, causing anxiety, depression, and even physical ailments like insomnia and high blood pressure, which can weaken you and make you susceptible to disease

Though a pessimistic attitude is harmful, there are times when a moderate amount of pessimism is useful:

• When you’re contemplating an investment, you’re more likely to scrutinize it to be sure it’s a solid opportunity for you
• When someone phones you with a deal that’s too good to be true, you’re less likely to fall for a scam
• When someone you know to be unreliable makes a promise, you won’t count on them, so you’ll create a backup plan; or you’ll be pleasantly surprised when they keep their word
• When you’re asked to take on a responsibility that you know is out of your skill set, you’ll find it easier to decline

Nevertheless, too much pessimism will affect you negatively. It’s important to change your mindset to allow for positivity. Some strategies to try:

• When something you anticipate being problematic actually goes smoother than you expected, celebrate it! Say out loud, “That went better than I thought it would.” Analyze what went right—the customer service representative knew just how to handle your concern (be sure to thank him); the miscalculation you made was caught and corrected before it had a chance to affect anything; the work product you thought was too ordinary turned out to be exactly what the client was hoping for. Then file your success in your memory bank to refer to when you’re in a similar situation.
• If you suspect your friends are avoiding you, do a little honest introspection. When you get together, do you vent your frustrations? Talk about all your problems? Shoot down possible solutions? Try this little experiment. Call one of your friends, and ask him something about his life. How was his vacation? What did he do, who did he see? Listen, and resist the impulse to steer the conversation onto a negative topic. Instead, ask more questions about your friend’s experiences.
• When you have to do something you’re worried about, instead of focusing on all the things that could go wrong, imagine what the best possible outcomes would look like. Is there something you could do to prepare for a good result? Maybe wear an outfit that makes you feel more professional? Do a little research or review policies? Tape an affirmation over your desk?