Your coworker may be acting out for reasons completely misunderstood. If possible, take some time to find out what's bothering him. If you find out that he's having health or family problems, you might change your perspective about him being "grumpy" -- he's just letting his personal problems overflow into the workplace. While that's not an excuse in a professional environment, you may find it easier to not take his insensitive remarks too seriously or personally.

Your grumpy coworker may seem rude and insensitive to you, but maybe in his mind he sees nothing wrong with it. Take a moment to put yourself in his shoes. If he always communicates in a loud, angry-sounding voice, perhaps that's simply the way he was raised. If he's from a different region of the country or the world, he may have completely different behavior expectations than you do. And sometimes different personalities simply see the world -- and thus behave -- differently. Try to be accommodating.

While few people enjoy confrontation, it may be necessary at work -- particularly with repeated offenses that are demoralizing people. Politely ask your grumpy coworker whether he realizes how rude he's being and explain how it affects you. You may be surprised to discover he has no idea how he comes across. If that's the case, you'll be doing him -- and the rest of the office -- a big favor.

Sometimes nothing you do or say will make a grumpy coworker act any nicer. You can't control him. But you can control yourself and the way you respond. Never step outside professional boundaries, gossip inappropriately or retaliate, as tempting as it may be. If necessary, find ways to keep your composure -- breathe deeply, take a short break or walk outside. You may need to be careful about how much time you spend around your grumpy co-worker to avoid triggering your own emotional responses.

If your grumpy coworker is seriously affecting your workplace's morale and performance, it is an appropriate reason to talk to your manager or human resources department. Try this angle if talking to your coworker on your own doesn't work or makes matters worse. Document as much evidence as possible, particularly if you feel like your coworker is harassing you in any way.

If nothing helps and your grumpy coworker is bothering you as much as ever, you must assess whether it's something you're willing to tolerate. You may be stuck with him as long as you're both working together, especially if he hasn't done anything that warrants termination. If putting up with him isn't worth the trouble, consider putting out your resume. Just remember that grumpy people are everywhere.