The people you surround yourself with directly affect your quality of life; that's not just good advice — it's been proven by social scientists. Whether you are trying to exercise more, find a job, or meet your match, it's more likely that you will achieve those goals if you are around friends with a positive attitude towards your plans — and their own.

Those who aren't supportive, those people in your life who actively discourage you, are toxic. Those friends may make you feel needed, like you are the only person who really gets them, but ultimately they step directly in the way of your forward-moving plans. 

Ideally, you can easily identify who those toxic people are, and take steps to unfriend them (I have done so twice in my life; it wasn't easy, but it was one of the best things I ever did). So, how do you know if someone is toxic or just going through a bad time in their life? It can be hard to tell when you see them regularly. Sometimes it can be tough to see someone's true colors when you are so close to them. 

Below are a few of the most toxic personality types; if you can identify them in people you know, you might want to consider how they are affecting your life. 

The Debbie Downer: This friend (which can be of either sex — the name is just a reference to the famous "Saturday Night Live" character — is the one who is just generally negative about everything. The person is probably not specifically negative about you (see Negative Ned below for a description of that character), but will tend to see the whole world as a bleak and horrible place with no opportunities for happiness. While we all have bad days (or even weeks), the Debbie Downer person sees the glass as half-empty all the time — and is trying to get you to see the world the same way. 

The Negative Ned: This person likely has trouble moving forward in his own life; and when you tell this person about positive plans for yours, he will actively discourage you, reminding you (or fabricating) all the challenges and difficulties in your plans. Friends who fit this description want to keep you right where you are — not moving forward in your life — just like them. 

The Party-Too-Heartier: The partier may have a substance-abuse problem — or they may just be trying to drink, drug or otherwise celebrate their problems away but aren't necessarily addicts. Either way, they're going to rope you into that fourth or fifth drink when you have plans to get up early the next day, or are pros at convincing you to skip work/a workout/class to go out and do something fun. It's great to have someone fun in your life, but that character trait can be deceptive if it ends up being a constant distraction to really living life (which is about more than partying). 

The Browbeater: This person relates to friends by bullying them. They may use social (or even physical) intimidation to get people to do what they want. It's never about what you need or want, it's about what this person wants — and you find yourself doing it because you're afraid of what will happen if you don't. You should nix this type of person from your life as soon as possible. 

The Underminer: This friend talks about you behind your back, mocks your workout plans, gets you to leave the career fair early because they have a headache, borrows money and doesn't pay you back, and tells you how you're not really capable of getting a better job. They can be funny, pithy and silly while they do all these things (or maybe droll and sly), but at the end of the day, this type of person is keeping you from your goals.

If any of the above describe your so-called friends, think again about how they may be holding you back. Assisting a friend in need is one thing, but being someone's receptacle for negativity, abuse, or inertia isn't helping anyone.  

Now go out and find some (healthy, happy) new friends!

Related on MNN: 

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.

5 types of toxic people to nix from your life
Are frenemies bringing you down?