You won't see the possibility of failure promoted officially in many process improvement text books, although the concept will be there under the acronym of PDCA. This is W.E. Deming's learning cycle of Plan-Do-Check-Act. It is probably the single most important concept to remember when attempting any process improvement and should be cast in neon lights in any organisation.
When enthusiasm or more often necessity takes over, the Plan-Do sections are completed and the Check-Act never happens. It's assumed that any change was an improvement, whereas the change may have been a failure. That can be a good thing, as it's an opportunity for learning something that you previously didn't know about the process. So just create a new PDCA cycle, based on your learning, and try again. The humble PDCA cycle can be used anywhere during an improvement project and in one of any size. It truly is the multitool of process improvement.