Your friends hung out without you and you feel left out, provoking jealous feelings. Jealousy stems from a feeling of insecurity and a fear of losing something important to you, according to GoodTherapy.org in the article, "Jealousy." Be careful not to let jealousy color your perception and thoughts and damage your friendships.

Acknowledge the Jealousy

It’s important that you be aware of your feelings of jealousy. If your friends went out for pizza without you, take note of how you feel, and face the jealousy. Be aware that having jealous thoughts does not make those thoughts reality, warns psychologist Robert Leahy in “Jealousy Is a Killer: How to Break Free From Your Jealous Feelings,” on the "Psychology Today" website. For instance, you may think, “They don’t want to be my friend,” but the reality is, getting pizza without you does not mean that.

Examine Your Feelings

Reflect on the underlying reason for your feelings of jealousy. Perhaps deep down you feel that you're not good enough. This judgement of yourself can result in feelings of inadequacy and fear that other people are better than you, invoking a worry that you will be replaced, and producing a feeling of jealousy, writes psychologist Margaret Paul in "Are You Jealous? Is Your Partner Jealous?" on The Huffington Post. Examine your feelings of jealousy and root causes by talking with a trusted friend or journaling as a means to connect with yourself. It's important that you learn how to handle your underlying issues so that they don't trigger feelings of jealousy.

Change Your Focus

When you feel jealous, you'll tend to focus on the negative. You may focus on the fear that your friends may enjoy each other’s company more than your company. Jealousy can cause you to make untrue assumptions and to take actions personally. Rather than listen to your inner dialogue and fears -- "They don’t like me anymore" -- tell yourself that it’s ok if your friends hang out together and that it doesn’t mean you are being displaced. It's common for a person to have various types of friendships and for each type to fulfill an important role in her sense of self, suggests licensed psychologist Patricia Leavy in "The Codes of Female Friendships: 5 Common Friend Types and Why We Want These Gals in Our Circle" on The Huffington Post. For instance, a person may look to one friend for advice and brainstorming, another to build her up, another for brutal honesty, another because she "gets" her and yet another who knows when to sit quietly with her. Your friends may be hanging out together because they fulfill an important role for each other that has nothing to do with how they feel about you.

Share Your Fears

It can be helpful to discuss your feelings of jealousy one-on-one with each friend. Do so when you are calm and have your feelings and thoughts collected. Avoid making accusations by using "I" statements. For instance, "I felt jealous when you and Emily went rollerskating and I wasn't invited. It made me feel left out." Be aware that your perceptions of the situation may be opposite of your friend's perceptions, asserts psychologist Clifford N. Lazarus in "Taming Jealousy," on the Psychology Today website. Perhaps they thought you didn't enjoy rollerskating and that's the only reason you weren't invited along.