Derek Handley's talk is worth watching:

I like his statement about five years:

19,392 is apparently the number of days that I have left to live.

And although it sounds like a lot, over the last few years I've come to realize that it probably takes you a good five years to achieve something meaningful. Turns out that 19,392 is really only 10 of those 5 year blocks. So when you think about having to achieve ten things and that's all you've got, you'll be much wiser in how you spend each of those chapters...

...When I was 21 and starting out, I was aspiring to be an entrepreneur, because I wanted to build businesses. I wanted to make a living, I wanted to make a mark, and I really wanted to make money.

Ten years on, after this period I started to see things very differently and I started to see entrepreneurship as one of the greatest assets of society to make the world a potentially better place. As an answer to many of the world's ills, and as an enabler to much of the world's opportunity.

Well said, sir. Well said.

Be useful.

Become great.

Be excellent.