Looking back all these years later, it is clear to me that the people I surround myself with are just like that fire.

A live coal placed next a dead one will either kindle that or be quenched by it. — Epictetus, Discourses XCIX

Either you become like your friends, or they become like you. We’ve all seen it happen to friends — they start taking on the habits and mannerisms of their partners. A lot is at stake. So, you should be careful about associating with people who won’t help better your position in life. And by position, I don’t just mean your financial status; I also mean your mental position.

“…you are the average of the five people you associate with most, so do not underestimate the effects of your pessimistic, unambitious, or disorganized friends. If someone isn’t making you stronger, they’re making you weaker.” — Tim Ferriss

Negative thoughts are contagious. A recent study from Notre Dame found that college roommates spread anxiety and negative emotional states to their roommates. Throughout their first year of living together, roommates begin to mirror one another’s actions. They pick up the habits of those they associate with most. This is a classic example of cognitive vulnerability being altered by social environment.

Other research shows how your social networks impact your weight, smoking habits, and happiness. For example, when one partner in a married couple quits smoking, the other is 67% less likely to smoke. Happiness on Twitter is contagious as well. It spreads up to three degrees from the original tweeter. The people you let into your life have a bigger impact on your happiness than you could imagine.

You probably spend the bulk of your day at work. Outside of your partner, the team you surround yourself with will have the biggest impact on your life. Do they make you better? Do they push you to take risks and grow as a person? Do you look forward to going into work every day?

If they don’t make you better — and if you don’t look forward to it — why are you still there? If the people you surround yourself with aren’t helping you grow, they’re holding you back, or at the very least hindering your progress. Pull off any log that smothers your fire. The longer you wait, the harder it will be to reignite the flame.