Learn to be Assertive and Love it!

Somebody cuts in front of you in the grocery store line. You're irritated but don't say anything. You disagree with your boss, but say nothing. Sound familiar?

You think: I'm confident, I'm smart, and I know what I want. Why can't I just say it? Being assertive—standing up for yourself and speaking your mind in a clear yet respectful way—can be remarkably hard on a good day. We worry if we ask for what we need, we'll put someone out. Or that we'll come across as a you-know-what. So we just let what we want go unsaid.

In your defense, it is more of a challenge to state your needs these days. The still-shaky economy may make you hesitant to ask for that raise at work.

The payoff of having your own back, though, is enormous. "When you say what you want, you live a happier and more authentic life," says Caroline Adams Miller, author of Creating Your Best Life. Those who speak up do better at work, have more time, and have healthier relationships.

So how do you master this crucial skill? "The three keys," explains Miller, "are knowing what you want, believing you have a right to it, and finding the courage to express it."

Surprisingly, your nearest and dearest can be the toughest to stand up to. "They're the people we want to please the most," says Miller. "We'd rather be unhappy ourselves than disappoint them." To complicate matters, we have to fight a lifetime of old (bad) habits—saying "sure" when we really mean "no way."

True, standing your ground can be momentarily uncomfortable, but it's so worth it—your relationships will be stronger as a result, Miller says. Try these tactics:

Your sister is always asking you to watch her kids; your running buddy keeps dragging you to Spinning class, which you hate.

The solution: Take a deep breath so you sound calm and just say, "No, I'm not able to do that," says Simon Rego, PsyD, director of the cognitive behavioral training program at Montefiore Medical Center in New York City. If she pushes back, repeat, minus a word or two. "No. I'm not able." This may go on for several rounds.

"Each time, you shorten the phrase until you eventually just say no," says Rego. "It's extremely effective because it allows you to convey what you want without getting upset."

You need your folks to respect your decisions about your kids; you want the in-laws to stop breaking the bank on gifts.

The solution: When you're broaching a sensitive topic, it's best to start with the word I. "I statements are expressions of your own needs, which we all are entitled to have," explains Rego. Using you statements, on the other hand, can put the other person on the defensive, which will only escalate an argument.

Keep it simple and own it ("I feel my kids act crazy when they eat candy, so I don't want them to have any.")

Maybe your friend always picks the restaurants (and pricey ones), or your man chooses your vacation spots every time.

The solution: This one pops up a lot in close relationships. Here, too, that I statement is key. Soften it with at least one thing the other person will be happy to hear ("Our date nights are so fun, but I would love to see a movie this time.")

Overdue for a raise? Longing for more interesting assignments? Working with spotlight stealers who are constantly broadcasting their accomplishments (and taking credit for some of yours)? You know what you have to do!

"Assertiveness is one of the most crucial tools for success," says Gabriela Cora, MD, a psychiatrist who specializes in workplace issues. "To be able to clarify a thought, make it precise and relevant, and share it at the right moment is an art." Luckily, it's a learnable art.

Consider this your cheat sheet for getting your needs met from 9 to 5.

Show your best stuff is yet to come. "You do need to present your case, citing two or three of the valuable contributions you've made to the company," recommends Dr. Cora.

But equally crucial, adds Dr. Cora, is to look ahead to the future: "Discuss the things you want to do in the future that are in line with your boss's goals." In so doing, you gain power in the negotiations, because you become more valuable to your manager. What if the head honcho flat-out says no?

Ask: "Can we talk about my performance again in six months?" You're not pushing; you're just showing that you believe in your skills enough to follow through.

Don't go first. Though you may think it's always best to get your idea on the table first, it's actually smarter to listen before you take the floor, says Dr. Cora. "Look to see how you can piggyback your idea with someone else's," she advises. Wait for two or three people to speak, then make your case, saying something like, "My idea, which works well with Sara's, is…."

Keep in mind that brevity helps, so make your case in three to five sentences, advises Dr. Cora: "When people don't feel confident, they tend to say too little or too much, and their point isn't clear."

The maître d' at a restaurant gives away the table you were next in line for. The guy using the treadmill before you leaves it dripping in sweat.

You'd think that speaking up with strangers would be easy—after all, you never have to see them again. But some of us actually have more trouble in these situations because we feel like our speak-out skills are on display.

Make it simpler with this advice.

Not sure how to ask for a refund on the top you washed once that promptly fell apart? Make what's called a "complaint sandwich", says Arthur Gallego of Gallego & Co. Brand Communications, which manages customer service programs for companies.

The layers of the sandwich, in order: a statement saying how much you enjoy the product or brand, then a description of the problem, then a statement that you hope the company/store can stand behind its products and fix the issue.

Sample script: "I shop here all the time, but I washed this shirt once and it came apart. I'd like you to replace it or give me a refund."

If you're not used to speaking your mind, your go-to reaction may be a pointed stare or loud sigh, but these nonverbal expressions of anger aren't going to help you get what you need—or make you feel good about yourself, notes psychologist Sharon Greenburg, PhD.

Better bet: State your case in a neutral tone (think TV newsreader) and reserve the eye-rolling for when you watch Jersey Shore marathons.

Empathize, advises Josh Denton, president of Denton Consulting Group, who consults with companies on customer service and human relations.

Say a fellow shopper snatches a marked-down pair of shoes out of your pile. Instead of snapping at her, put her move in context. A simple "Wow, this sale is crazy!" before pointing out that those heels are yours helps you get what you deserve—in the most pleasant way possible.