Implicit memories are not necessarily repressed, nor are they necessarily the result of trauma. They are weakly encoded memories which can affect conscious thought and behavior. Retrieval cues do not bring about a complete memory of some events because most of the event was not encoded. Daniel Schacter and Endel Tulving introduced the terms 'implicit memory' and 'explicit memory' in their attempt to find a common language for those who believe there are several distinct memory systems and those who maintain there is only one such system. Most lost memories are lost because they were never elaborately encoded.
Perception is mostly a filtering and defragmenting process.
Our interests and needs affect perception, but most of what is available to us as potential sense data will never be processed. And most of what is processed will be forgotten. Amnesia is not rare, but is the standard condition of the human species. We do not forget simply to avoid being reminded of unpleasant things. Long-term memory requires elaborative encoding in the inner part of the temporal lobes.