Sometimes it's really uncool to say no.
It's especially "uncool" to say no when you're trying to fit in, or you're learning the ropes at a new school or job. You just want to be accepted, and you don't want to seem like a downer. But the truth is that life is not full of sunshine and rainbows, and while it's nice to say yes when you can, there are plenty of times when saying no is the best thing you can possibly do.
1. When you are overwhelmed.
Just this week you've had reading in three different textbooks, twenty pages each. On top of that, you have 30 questions of math homework, two essays, one poster project, and a Powerpoint due tomorrow. Oh, and don't forget practice for band/choir/theater/debate/basketball, etc. Tonight you have a four hour shift and you're probably going to get a half hour of sleep. You've got your work cut out for you, and though it may be temporary, saying no to everything else will make your life easier, and you will be able to breathe and know you did the best you could. So if your friend asks you to come watch a movie in their dorm room, you're not going to say yes. You're going to say, "Sorry, I can't. I am overwhelmed." And if they don't thank you for being totally honest, they're not your friend.
2. When you are physically ill.
If you have snot running down your chin, your temp is anything over 99 degrees Fahrenheit, or you have a headache that's stronger than a double dose of Ibuprofen, it's okay to skip going out to pizza with your friends. If you have chronic migraines, it's fine to turn people down to going out and sit in your room with the lights out. Don't sacrifice your health just to have a good night out because if you get sicker, you'll regret it. You also run the risk of slowing your healing. If you absolutely need company, ask a good friend to come by with a short movie, a can of chicken noodle soup, and whatever medicine you need to be comfortable. Bonus points if they provide a huge cuddly blanket.
3. When it will set you off.
You know yourself well enough to say that certain things are going to bother you. If you are an introvert, or you have anxiety, or you have agoraphobia, you're not necessarily going to find solace in human interaction. I'm also talking to those of you who have trouble getting along with people simply because you don't like them. You don't have to force yourself to interact with people you don't like, people who drain your energy, and you don't necessarily have to explain yourself either. All you have to say is, "I don't feel like it." If someone is really close to you, they will understand. And if they're not close, and they don't understand...who cares?
4. When it goes against what you believe.
If you are strongly against the use of alcohol, you don't have to spend time at a party with a bunch of people who are downing it. If you are an atheist and you feel uncomfortable in a church, you don't have to hang out with friends who spend three days of the week there. I'm not saying to be snobbish and ignore people because they think or feel differently from you. What I am saying is that you can choose to stay in your comfort zone. Sometimes that's not a bad thing.
5. When you just don't feel like it.
You don't need any reason to not want to do something, and you don't have to explain yourself. You may owe an explanation to your closest friends, but it's your life. How you spend your time is vitally important. If you don't think it's going to be beneficial to you, and you have other goals you'd like to spend time on, don't settle for less than what you want. Be true to yourself is always the best answer.