Is there someone you could ‘report’ to daily? Having that person keep you accountable might help. I guess it’s similar to having a buddy as @inky suggested.

And how about setting it up so that if you skip a day (as long as it’s not because of illness etc), you have to do something you really wouldn’t like to do: singing in front of a group of people, dancing in the middle of a busy supermarket; anything you would rather avoid. Maybe eat fish eyes!

IF you really don’t want to do that thing come the end of the week, just keep up with your daily exercise. Of course, you could always lie but then that would be on your conscience and you know you would be cheating no-one but yourself.