Swami Gulagulaananda said:
"Don't be the rooster who thought he caused the sun to rise"
Well, simple is the quote, and simple is the moral... "Self importance" is a quality which all of us possess. But it's wise to know how good you really are. Everyone thinks he/she is the greatest person in the world - nothing wrong in it. But you should also know your strengths and weaknesses. Everybody cannot be perfect in everything. So, in case you are in a group, and you feel that the group will not function without you, then you are wrong. A small fable, quite old, is here:
"An old woman had a rooster which crowed every morning. All the villagers used to tell the old woman - 'If it was not for your rooster which wakes us up, we would still be sleeping lazily and would have wasted a lot of precious time.' Now after some time, the old woman had developed a strange feeling, she thought that the entire village can function normally and smoothly only because her rooster wakes everyone up. She felt powerful, and she thought of demonstraing her powers... She killed the rooster, for she wanted to see the entire village frozen, the people continuing to sleep through the day. The next morning, she woke up and saw that all villagers were up as usual, and were performing their daily chores. Alas! The old woman had lost her rooster for nought."
Everyone is important, some more important than others in some field(s) - But nobody is so very important that people will leave or give up their ego and start licking your boots. You can see this not-so-pretty scene when kids play cricket - when the hotshot batsman becomes out, he says, "Not out!" And when others start fighting, he says - "Fine, then I'll go home taking my bat and ball." Kind of blackmail, many might relent to prevent the ending of the game prematurely. But this trick cannot be pulled on till eternity. After some time, the other boys will get frustrated and will ask the hotshot dude to walk home...
You should know exactly how important you are - I am not saying don't pull this trick at all, pull it as and when you need it - being careful not to stretch it beyond limits. Or you too will be asked to go home. Self importance and vanity are different. One should have self importance, but not to the extent of being egocentric or vanity. If you don't possess this uality, you'll end up being a door mat, on which everyone will rub their shoes.