This article is written by Amy Morin and first appeared in Huffington Post.

The company you keep says a lot about you. Friends have a big influence over how you feel, think, and behave. Here are five reasons you should be careful who you surround yourself with:

1. Strong-willed friends can increase your self-control. If you struggle to resist temptation, surrounding yourself with people who possess a high degree of self-discipline can help. A 2013 study published in Psychological Science reports that when people are running low on self-control, they often seek out self-disciplined people to boost their willpower.

Since self-control is vital to reaching long-term goals, befriending people with willpower could be the secret to success. Whether you’re tempted to skip that workout at the gym, or you’re considering blowing this month’s budget, spending time with a disciplined friend could boost your motivation to maintain healthy habits.

2. Fewer friends increases the likelihood you’ll take financial risks. When people lack adequate social interaction, they’re more likely to take bigger risks with money, according to a study published in the June 2013 issue of Journal of Consumer Research. Researchers discovered people who feel lonely or rejected were most likely to take the biggest financial risks.

Whether you’re dealing with a recent breakup, a fallout with family, or a failed business venture, be aware that your emotions could affect your spending habits. Uncomfortable emotions can increase the chances that you’ll behave recklessly, which may have a negative impact on your bank account.
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3. Too many social media connections can increase your stress level. When it comes to social media, “the more the merrier” may not be the best approach. A report from the University of Edinburgh Business School says that more Facebook friends means more stress. Researchers linked an abundance of social media connections to increased anxiety about offending people.

The increased stress stemmed from people’s desire to present a version of themselves that was acceptable to all their social media contacts. While your college buddies may enjoy publicly discussing that “weekend in Vegas,” your parents and co-workers may be less than impressed by those stories. So before you begin adding people to your social circle, remember the potential downside to having too many friends on Facebook .

4. Close friends could be the secret to longevity. When older adults have close confidants, they’re likely to live longer, according to a 2005 study conducted by Australia’s Flinders University. After following 1,500 people for 10 years, researchers discovered that people with a large network of friends outlived their counterparts by 22 percent.

Other studies touting the health benefits of friendship have shown that friends lower the risk of disease by reducing blood pressure, heart rate, and cholesterol. So while it may be tempting to think that friends are sometimes more trouble than they’re worth, clearly, having close friends can be one of the best things you can do for your health.

5. Friends can greatly influence your choices. A 2014 study published in the Journal of Consumer Research found that friends often bond by providing one another with moral support to resist a temptation. However, friends also commonly conspire together to enjoy indulgences. Researchers discovered that when it came to resisting temptations — like eating chocolate — sometimes friends were more likely to become partners in crime as they decided to indulge together.

Your likely to start acting like the people you surround yourself with. Pick friends who make poor choices, and you could get dragged down fast. But, if you choose friends who inspire and challenge you to become better, you’ll increase your chances of reaching your goals.

Amy Morin is a psychotherapist and the author of 13 Things Mentally Strong People Don’t Do, a bestselling book that is being translated into more than 20 languages.