From Stepping Stones, a book-length collection of interviews with Seamus Heaney by Dennis O'Driscoll.
The thing I should say, however, is that I am always nervous before a lecture. Even in my fifties, in Harvard, if I had a lecture, I'd be up early to try to get it squared out in my head - not that I could ever quite manage to do so. Lecturing week after week, as part of the padagogic routine, is more of a test than people realize. In the end, the most important thing is to be in good physical and mental shape. You can prepare as much as you like and amass material galore, but unless you come in fresh. like an athlete on to the track. you aren't going to do the job required. At the end of a lecture, I tend to be as sweaty as a sprinter at the end of a race. [Stepping stones: interviews with Seamus Heaney, p.104]