'Who are you? said the Caterpillar.
...
Alice replied, rather shyly, 'I - I hardly know, sir, just at present - at least I know who I was when I got up this morning, but I think I must have been changed several times since then.'

'What do you mean by that?' said the Caterpillar sternly. 'Explain yourself!'

'I can't explain myself, I am afraid, sir,' said Alice, 'because I am not myself, you see.'

Lewis Carroll
Alice's Adventure in Wonderland