1. Chew gum. 

Strange as it may seem, chewing gum -- not to mention the fun of popping bubbles -- has been shown to improve reported mood as well as lower cortisol levels.

2. Surround yourself with plants. 

Immersing yourself in nature can make you feel happier, and even just a little exposure can help you relax. One study at Washington State University found that entering a room with plants can lower your blood pressure and increase your productivity. Plus, plants increase oxygen, helping you breathe easier.

3. Mow the lawn. 

A chemical released by a mowed lawn causes people to feel happy and relaxed, according to research. Another benefit? Getting a chore out of the way -- and off your mind.

4. Listen to classical music. 

Music can brighten up your day, but it turns out there's also a physiological impact to listening to music: One study found that listening to classical music lowered participants' blood pressure, slowed their heart rates, and reduced levels of stress hormones.

5. Pucker up. 

Sometimes feeling weak in the knees isn't a bad thing. Kissing releases oxytocin, a chemical that reduces levels of the stress hormone cortisol.

6. Reduce your screen time, especially before bedtime. 

Spend the majority of your day sitting in front of a screen only to go home and stare at another screen (or two)? That artificial light can mess with your melatonin production and alter your circadian rhythms, which can impact your sleep. Young adults in particular are likely to be affected. Studies have shown that teenagers who use their phones late at night are more likely to be depressed.

7. Drink some tea. 

Scientists at the City University of London found that a single cup of tea reduces stress rates by as much as 25 percent. And certain types of herbal tea, like green tea, contain L-theanine, which has also been shown to reduce stress.

8. Put your head in a paper bag. 

It's become a bit of a joke, but it turns out breathing into a paper bag will actually make you calmer. Research suggests that since when people feel anxious they often breathe too quickly, their bodies build up an overflow of oxygen. Breathing into a bag for half a dozen breaths increases the amount of carbon dioxide in your body and helps you feel better.

9. Grab some chocolate. 

It's not your imagination: You do feel better after eating chocolate. Even eating just 40 grams, lowers your amount of stress hormones.

10. If life gives you lemons, make lemonade. 

If chocolate isn't your thing, try citrus. Scientists have found that vitamin C helps regulate cortisol and prevent blood pressure from spiking.

11. Have a laugh. 

Watching funny videos -- and laughing -- physically helps you relax by releasing endorphins, the brain chemicals known for their happy fuzzy effect.