3. Gripe:Your boss hands you an unexpected assignment that needs to be finished by the end of the day.

What to do right now: While it's okay to feel frustration, anger, and even fear, it's not good to stay with those feelings for long. Negative moods are associated with negative outcomes like impaired performance. Take a few deep breaths to take control of your body and mind, and then say this to yourself: "I can handle this; it's a challenge rather than a threat." Reminding yourself of other times you've performed well under pressure will help you realize that you can do it now, too, says Rossman.

More from Prevention: What Kind of Angry Are You?

Be prepared for situations like this in the future by keeping relaxing scents stashed in your desk drawer. Mixing lavender with bergamot oil decreases anxiety. Add the synergistic mixture to a room diffuser (like the ScentBall™, available at amazon.com) to fill your workspace with a relaxing aroma. Or just sniff lavender on its own to enhance concentration.

4. Gripe: It's late afternoon and you're ready to crash.

What to do right now: Have a mood-boosting snack. There is a bump in melatonin, the hormone that naturally puts your brain to sleep, between 2 and 4 p.m., says Drew Ramsey, MD, assistant clinical professor of psychiatry at Columbia University and author of The Happiness Diet (Rodale, 2011). To increase your productivity and fight off that slump, try mixing healthy sugars and fats like goat cheese on cherry tomatoes, almond butter spread on a banana, or even a cup of green tea with a teaspoon of honey, he says.

More from Prevention: 13 Foods That Fight Stress

And if you don't have snacks on hand -- jump up and down! It may feel goofy, but it works. "As adults, we're so earthbound; something about getting your feet off the ground and doing something childlike can give you the quickest jolt of energy and good cheer," says Rubin. If you're afraid of looking silly, take five minutes to run up and down the stairs or go for a quick walk around the block -- even short bursts of exercise can increase levels of serotonin, those brain chemicals that make us feel good.

5. Gripe: The friend you've been trying to get together with for months cancels tonight's plans.

What to do right now: You might feel resentful and disappointed, but take a moment to consider that there may be a lot going on in her life that you might not know about, suggests Rubin. If you're leaning toward confrontation, have a small nosh rich in the amino acid tryptophan: researchers found it can significantly decrease quarrelsome behaviors while increasing agreeable ones. Tryptophan-rich foods include dried chia seeds, chocolate, oats, bananas, dried dates, milk, cottage cheese, turkey, and peanuts.

More from Prevention: 8 Friends Every Woman Needs

Then make sure you reschedule that get-together. Nurturing friendships helps not only your happiness, but your health, as well. Research has found that strong social connections can actually make us less susceptible to colds.