Despite being composed of just two little letters, the word "no" is both extremely powerful and extremely hard to master. Sure, you can pronounce it just fine, but actually getting it out of your mouth at the right moments is often one of the hardest skills for newbie entrepreneurs to learn. Nevertheless, it's a skill that's essential for success.

Learning to say no strategically increases your productivity, clarifies your priorities, and ensures you have the time you need to devote to the people and projects that are most important to you. A good place to start is a simple "not-to-do list" that cuts suboptimal practices and common time-sucks out of your day. But according to hedge fund manager and entrepreneur James Altucher, you need to go deeper than that, by learning to say no to whole categories of destructive experiences and people.

That's the underlying principle of his new book, The Power of No: Because One Little Word Can Bring Health, Abundance, and Happiness, which he wrote with his wife, Claudia Azula Altucher. So what sort of harmful aspects of life do you need to learn to refuse? Altucher recently offered a sneak preview of his ideas in the form of a Slideshare presentation. Here are some of the things he feels you should start refusing right now.

1. Social pressure

"When we were children," Altucher writes, "we were taught to be polite, to be nice, and to say yes at all the wrong moments. This leads us to be pressured by colleagues, institutions, bosses, friends, and family to attend to their needs." You want to be kind (see point 7 below), but you don't want to be a doormat. To get this balance right, Altucher advises that you follow a simple A-B-C procedure: acknowledge what you're being pressured into, set your boundary, and then close (i.e., stick to it).

2. Negative chatter

Many people are less kind to themselves than they are to others. Stop indulging in this negative self-chat and turn off the nasty voice in your head asking, "Do I look ugly in this?" or "Why is work so miserable?" or even "Geez, that guy looks like a total idiot."

3. Jealousy

OK, probably you will never totally conquer jealousy, but you can say no to jealousy's making you miserable. Instead of letting feelings of envy impact your life, take a moment to examine what those feelings say about your goals and worries. "Jealousy is a guide to what's going on inside you," Altucher writes. "It's never about the other person." Use your jealousy to clarify what you want and what you're afraid of and say no to being ashamed of it or whatever it is you think you lack.

4. Thought attacks

Altucher confesses to being one of those people who often wake up with worry at 3 a.m. Just say no to these sudden "thought attacks," he advises. This type of panic accomplishes exactly nothing. "Looking back, nothing that I predicted at 3 in the morning ever happened," he says.

5. Bad luck

Bad luck isn't something you're cursed with. It is something you do--a way of approaching life and shutting down (or entirely missing) opportunities. Therefore, you can simply refuse to wallow in bad luck (and even train yourself to be luckier).

6. Draining people

It's simple, Altucher insists: People either support you or drag you down. For each person in your life, identify which camp he or she belongs to and, for those you place on the wrong side of this fundamental divide, it's time to start saying no to invitations from them.

7. Selfishness

Think being "me first" is essential to success? Not at all. The genuinely accomplished are almost always motivated by a desire to be of service. So stop thinking ruthlessness underpins success and start saying no to selfishness. Try this trick, Altucher suggests: Though it might sound morbid, make it your intention in everyday interactions "to treat people as if it were their last day," and see what happens.

Would you add anything to this list?