Below is the link to a video commencement speech by JK Rowlings, the author of Harry Potter series.
She was a dismal failure earlier in her life -- divorced, jobless & failed to achieve her dreams. But through her determination & imagination, she made it.
She speaks with clarity, sincerity and an unassuming humour too.
The video is a great motivational video for teachers & students. There's a complete transcript of her speech at the site as well.
It's brilliant - moving and inspiring.