For people who are creative writers and willing to help...?

I have signed up to give the Farewell Address at my high school graduation - I normally am a very creative writer who can (in an instant) come up with stories that are quite good, but for some reason I am having lots of trouble getting started with this speech. I don't have a plot or anything about what I should be writing about so I guess that could be what is getting to me. If you could please advise me on what it is I should be addressing and maybe provide a few examples I would be grateful.