If you recalled traumatic events on your own, outside therapy, they are reliable because you could not have been led into them. They are led into this false belief system just as surely as in formal therapy. All good therapy takes a long time and involves delving into the past. The forms of therapy that have proven to be the most effective are cognitive and behavioral therapy that do not dwell on the past, but help clients cope with current life stressors, often by reframing the way they perceive their problems. 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.