The learning never stops. This is just the beginning.
Your gifts and talents were given to you for a reason. They are worth far more in the service of others.
I hope that somewhere along the way you will lose. So you learn humility.
I hope that you are betrayed. So you will value friendship.
(And on and on along those lines........)
At every graduation I've been to I have heard a happy face pump-up speech, that was about as fulfilling as a Chinese meal one hour later. Otherwise looking back on the past is cool, as long as you're doing something with it today. My two cents. Below is a link where you can find a link to a real barn burner.
A 2005 address championing the liberal arts might be the best graduation speech of all time