Can you tell us how/in what circumstances you 'suddenly lost' your password? It may still be on your pc somewhere (though hidden from you) and we might be able to help you recover it.
Most people write down their passwords etc using pen and paper and keep it safe for just this sort of occasion.
What O/S are you using? (XP, Vista, W7)
What email client on your pc? (Outlook Express, Windows Mail etc.)
Or are you using gmail Webmail only? (via your browser Firefox, IE8/9 or other)