<i>So here it is, the most plain, powerful, single word you have to know, and use when managing a project: NO</i><p>If you aspire to mediocracy in an enterprise, then this <i>may</i> help you survive.  Otherwise, it's horrible advice.<p>If you have serious competitors, then you have to find YES.<p>If you are attempting to do something extraordinary or for the first time ever, then you have to find YES.<p>If you are building a startup, then you most certainly have to find YES.<p>I am <i>not</i> saying that all things are possible.  I am saying that you need to find YES.  Once you get into the habit of saying NO, you forget how to find YES.<p>A simple (and timeless) example.  Your customer wants Deliverable X in Time Y using Resource Z.  You know it's too much and will disappoint.  So instead of saying NO as OP recommends, you find a way to do what can be done.  It may have a few less features, may need an extra resource, or may take a little more time.<p>Or better yet, you analyze the constraints long enough to find methods or tools you hadn't considered to say YES to all of it.  (We never would have found Framework ABC if the customer hadn't forced us.)<p>I have often been to only person finding YES when I was surrounded by others preprogrammed to saying NO.  That's how they survived.  Usually in an enterprise or institution.  That same thinking is a disaster in an achievement oriented environment.<p>Finding YES forces you to stretch beyond your previously perceived limits.  Settling for NO dooms you to mediocracy forever.<p>Some may call this a semantic argument.  I call it state of mind.  How badly do you want it?  Find YES.