That still means you're trying to predict user behaviour based on a predetermined set of positive behaviour signals, which in turn means you need to accurately know what every user is thinking every day, which is impossible.
Behaviour can be affected by weather, good or bad news about the economy and so on. When behaviour changes it doesn't necessarily change for all sites in the same way either. You just can't predict or guess how user behaviour will change from day to day. There are too many factors affecting people's lives.