Because you'll never get past your own limitations if you don't and you will plateau. It's inevitable--for me, my weakness is the having the patience for details. I'm terrible at this--put a spreadsheet in front of me and I zone out; expect me to sit through a 3-hour meeting and you have 60 minutes of interaction and about 120 minutes of unengaged head nodding.
In order to continue to grow as a professional, you have to recognize these weaknesses, and dare I say it, embrace them sometimes. These weaknesses can help you recognize how to surround yourself with the right people--whether they are direct reports, mentors or leaders. You can continue to learn from them. Not everyone can, nor should everyone be the CEO of a company, but by not only capitalizing on your strengths while working on your weaknesses, you can become an integral and invaluable part of a successful team.
Once you shut down and believe you know everything--AND you're exceptional at everything--that's the moment you stop growing...and watch the others pass you by.
