I found that certainty was not the most helpful barometer to use in trauma work. The objective reality of memories is inherently misleading: multiple people experiencing the same event together will usually have different memories of the event. Memories are a mix of perceptions colored by inner experience as much as by external experience--maybe more so. I think anything your mind produces is worthy of discussion, not in order to determine a degree of objective certitude, but to increase self-perception. There's always emotional truth to memories, regardless of the source. The only caution I think is to not treat any one memory as somehow more defining of your life or self or relationships than other memories.