呵呵...

Luke: Master Yoda, you can't die.
Yoda: Strong am I with the Force, but not that strong.

Yoda: That face you make... look I so old to young eyes?
Luke: No. Of course not.
Yoda: I do. Yes, I do. Sicker I become, old and weak... When nine hundred years old YOU reach, look as good YOU will not, hmm?