Definition of before one knows where one is (or before one knows it) in English:

before one knows where one is (or before one knows it)

phrase

informal
  • With baffling speed.

    • ‘Sure, sometimes the days crawl by, but before you know it, two months will have breezed past in the blink of an eye.’
    • ‘And waiting until you're a legal adult isn't so bad, you'll be one before you know it.’
    • ‘But when you're young, time seems endless and before you know it years have sped by.’
    • ‘By following these tips, you'll find your muscles will grow bigger and stronger before you know it.’
    • ‘Get in debt with your mortgage and before you know it, your nightmares will have spiralled out of control.’
    • ‘Then, before you know it, the pavilion seats were all sold out, and it was too late.’
    • ‘If they split up, he'll be on your doorstep before you know it.’
    • ‘A week passed and before they knew it, it was time for Adam to leave.’
    • ‘The school day flew by and before she knew it, Amy was walking home from the bus stop.’
    • ‘A report from an expert consultant could well be £400 to £600, there are solicitors fees and medical costs and before you know where you are it's up to £1,000.’