Such therapy can often be short-term. Memories are always accurate. All memories are reconstructions of likely scenarios in which you fill in the gaps. Thus, all memories are somewhat inaccurate, though they serve us well enough under normal conditions. Under severe social influence, however, memories can be distorted or even entirely rewritten.
Memory is largely a matter of rehearsal.
The more often a scene is rehearsed, the more real it becomes to you. Experiments have shown that people can be induced to remember events that did not occur. If you have a tiny intuition or a feeling that you may have been sexually abused, you probably were. If you were truly sexually abused, the odds are very good that you would remember it all too well. Repeated trauma is so distressing that it must be repressed or dissociated.