Jim Collins explains in five stages how top performing firms fall. This is a well known and quite obvious process, almost an archetype from Greek epics, but it is very easy to forget this process on the field. I think it is a good framework to serve as a guidepost when considering whether to act on signs of problems with a business or keep ignoring them.
1. hubris of success
2. undisciplined pursuit for more
3. denial of risk and peril: gathering wind, coming storm
4. grasping for salvation: a process of denial takes hold and the fall happens
5. capitulation: most fall but not all, and you might even be able to come back