I came across two videos I found inspiring: Chad Fowler's Don't Follow the Lemmings, and Randy Pausch's Really Achieving Your Childhood Dreams.
The two presentations have similar messages. Pausch's message is this: Brick walls are not there to keep you out. They are there to test your determination. Fowler's message: A lot of external obstacles are more perceived than real. The only real obstacle is doing the actual work.
Fowler's presentation is more aimed at software developers, but I think they're both suitable for a general audience.