I've visited the site every day for the past couple of months, every morning like clockwork. But today when I visited, my consecutive day count had been reset. How does the consecutive day counter work? Are there any known issues with it?
StackExchange days change at 00:00:00 GMT every day.
Looking at your history I see no access on October 21st. Looks like you had a string of consecutive days dating from August 24st up until October 20th.
Check what time zone you are in to see when the StackExchange day is for you.
There is some more information on meta.stackoverflow.com under the Enthusiast and Fanatic badges.