The saying goes, it's nice to be important, but it's more important to be nice.
This is wrong. It's more important to be important. From there, you can choose to be nice. Or not.
[shareable cite="@DreAllDay"]It's more important to be important.[/shareable]
Important vs. Nice
Which one would you rather be?
Important: of great significance or value; likely to have a profound effect on success
Nice: pleasant, agreeable, satisfactory. 
Important objectives get prioritized. Nice tasks may get noticed, then fake-smiled at and forgotten.
Important people are seen and heard. Nice people could also be important, but if not, nice people are ignored and forgotten.
Important engagements are marked on calendars and attended. Nice engagements are passed over and ignored.
'Being important does not mean you don't have compassion, or that you don't care for others. Importance means you know how to get seen, heard and known. You get things done the way you want them done. You know what you want, and you figure out bow to go get it.
Significance
Important is significance. Every person needs - not wants, but needs - significance, attention and success. No one needs anything at a satisfactory level. Important things may require you to be not-so-agreeable at times to make sure you get what you want. Nice people, by definition, have a problem with being disagreeable and thus my have to settle for less than what they want.
Important people create a position of power for themselves, from which they can do many nice and even great things. Things like helping their families, communities and even mankind as a whole. Would you agree that doing these things is important?
A person who achieves agreeable, satisfactory success probably can't help himself much, let alone his family or community. Satisfactory levels of value won't get anyone's attention, time or money. Pleasant ideas don't disrupt the world and make change happen. Many nice people, experiences and things don't get remembered.
And what we don't remember is obviously not important.