When you're asked to do something, go somewhere or help out, what is your default answer? If you're like most people, it's something like, "sure thing" or "you've got it" or just a simple "yes." And why not? It's good to feel wanted or to be needed—especially when it comes to your job. And saying "yes" to things supports collaboration and risk-taking. But here's the ugly truth: you've got to be a little stingy with your time.

Because time is the raw material of creation and contentment. You need those minutes and hours if you want to find solutions to problems or become an expert at something through study and practice or merely have the time to relax and recharge your batteries. You need to be as frugal with your time as you are with your money. Would you give twenty bucks to everyone who came by or emailed you asking for it? As Austin Kleon astutely puts in his book, Show Your Work, "Be as generous as you can, but selfish enough to get your work done."

Renowned management guru Peter Drucker was once asked to collaborate on a book about creativity. He famously responded: "One of the secrets of productivity is to have a very big waste paper basket to take care of all invitations such as yours—productivity in my experience consists of not doing anything that helps the work of other people but to spend all one's time on the work the Good Lord has fitted one to do, and to do well."

Of course, being on the receiving end of a "no" can be disheartening, but saying "yes" to everything can have brutal consequences. It's only going to make you more stressed out. It can also make others value your time less. Especially when you're starting out, it's easy to want to get involved in everything and show your willingness to learn. But if you overextend yourself, you'll find that the quality of your work suffers, your ability to learn gets sapped and you're left with little to no time for yourself (and the things you truly care about).

Be firm and decisive with your refusals and the reward is more time to focus on your work, off-duty passions and loved ones. You're also likely to gain respect for your candor. Of course, it's easier said than done, but here are a few tips that may help.

How to Say "No"

Don't stall.
Tell the person you can't do it, and politely decline right away. That way you don't drag out your discomfort or hold up the other person's plans.

Be honest.
Tell them why you don't think this is right for you. Or just explain that you have other commitments and can't make it.

Ask for a raincheck (when applicable). There are times when you'd really like to do what is being asked of you, but simply don't have the time right then. Offer up a plan for the future, in order to show good faith.