You have a n day streak! Write a program that keeps track of the number of consecutive days it has been run. 

The day resets at midnight (the local time of the computer on which the program is run). 

If there is a day that the program is not run, the counter is reset to zero. 

Every time the program is run, the counter should go up by one day if it is the first time the program is run that day. This means that the first time the program is run, it should say, "You have a 1 day streak!"

The output of the program is in the form: You have a [streak_length] day streak!

You are allowed to store data externally or modify the source code––your choice.

This is code-golf, so shortest code in bytes wins!
Bash, 102 bytes

find ! -newerat 0-1day -delete
touch -a a
echo You have a $((1+(`stat -c %X-%Y a`)/86400)) day streak!


Warning, do not run in any folder you care about. It deletes any file not accessed in the last day in the working directory.

Uses a file a to store data, using the accessed/modified timestamps.