One who is "sayyi.ul-hifz" is the one who is mistaken more than he is correct.
There are two types:
1. One whose memory was always bad throughout his life.
2. One whose memory became weak, either due to old age, he became blind, or his books were burnt (this type is called al-mukhtalat).
The ruling for their narrations:
1. For the first type, his narrations are rejected.
2. For the second type, then:
1. what he is known to have reported before the "ikhtilat" is acceptable.
2. what he reported after the "ikhtilat" is rejected.
3. that which is not known whether it was before or after, then judgement is suspended until it is clear which is the case.
(The above short notes are extracted verbatim, except the underlined part, which I added, from Tayseer Mustalahil Hadeeth, written by Dr Mahmood at-Tahhaan)
1. The short extract above briefly tells us the need to write more if we have a short memory span.
2. It always startle me when I try to recall a memory from the past, I always try to equate it with something totally different from what it was supposed to be.
3. Emotion plays a big part in our memory relapse. Due to our emotional attachment, our facts become massively distorted from the truth.
4. For a quick example, when asked about her present state of marriage, one girl rejoiced immediately and told the questioner with glowing excitement that she was always happy with her state of marriage from the start.
5. Well, that is further from the truth. She is happy now, but not then. In fact, in the early period of her marriage, she was clearly unhappy and poured her disappointment to somebody (which unfortunately was the questioner himself). Over time, her marriage becomes a lot better and she unconsciously loses her early memory of her disappointing start to her marriage.
6. Sometimes we have a reservation about something...be it towards people, situation or our own feeling. Almost all of the time, we tend to forget it when things get better. When these things rear their ugly heads and come back to haunt us, it's maybe too late to turn things around.
7. So to avoid this distorted truth, write more. I am always interested by truth and emotion, but for me, truth always comes first before emotion.