Control your emotions about the ending friendship so that they don't get the best of you. Ryan Blair, CEO of ViSalus and writer for Forbes, recommends compartmentalizing situations to stay on top of your professional game. Isolate the issue of the problematic friendship in your mind, keeping it separate from your work responsibilities as well as from home life. Give the problem thought only when you are choosing to do something to deal with the situation.

Maintain your professionalism. Resist the urge to badmouth your former friend or you risk gaining a reputation as a gossip and becoming an object of water cooler talk yourself, advises Jan Yager, Ph.D., author of "When Friendship Hurts: How to Deal With Friends Who Betray, Abandon or Wound You." If you must talk about the friendship, ask a friend outside of work to lend an ear instead of confiding in a a work buddy.

Find positive ways to channel any resentful energy you may harbor toward your former friend. Yager suggests investing additional time and effort in existing friendships or making new friends. Ask a colleague you'd like to get to know better out to lunch or schedule an after-work happy hour date with a friend you rarely see. Doing so will help take your focus off the failed friendship.

Treat your former friend with courtesy at all times. Resist the urge to adopt a snide tone or make sarcastic remarks when speaking to or about the person. Remember that the end of the friendship has affected this person as well, and overlook any inappropriate behavior on his or her part. Taking the high road will help protect your professional reputation.

Accept the emotions you have about the friendship. Feeling hurt or angry is normal. If you find yourself ruminating about the lost friendship, focus on what the friendship taught you about relationships rather than on the negative aspects of the friendship. Take the lessons learned and move on, resuming a productive work life.