Analyze the following passages:

“For last year's words belong to last year's language
And next year's words await another voice.”
— T.S. Eliot, Four Quartets

“No man ever steps in the same river twice, for it's not the same river and he's not the same man.”
— Heraclitus

What central theme connects the ideas expressed in the passages by T.S. Eliot and Heraclitus?