Weena - You might want to go back in the earlier posts on this thread to find some answers. We can have any number of blocks, but it's typically some form of doubt/fear. I would call on either the Akashic Record master or one of your guides to help - and do this at the beginning of the process. I use preparation techniques to build up your energy (i.e. prayer, chi building exercises), a deepening technique (i.e. trance induction to move into the pre-conscious state while staying awake), and an accessing script (i.e. sacred visualization involving a temple/library).
On past lives - perhaps starting with asking about a lifetime that is more uplifting to start with would be easier, then you can dive into the more intense lives. You won't see/feel/experience anything that you're not ready for.
Alena - The degree that it will prepare each person depends on the body/soul combination and how much conflict they have. If a person has had several lifetimes honing and using a certain talent (i.e. warrior, scientist, healer, intuitive, leader), and then comes into a body that also has similar abilities genetically (i.e. mother was an intuitive, etc), then the combination could be amazing. You can get someone of the caliber of Mozart, Newton, Nostradamus.
For this particular person, even if he doesn't remember the details of this current life, he will likely still have an instinctive sense (brought from his soul's memory) of clarity, how to lead soldiers/villagers, help them face their own fears, rally the troops, manage the village, etc - even without training. We all carry the memories of all our lifetimes.
If he does remember the details, then the results could be even more amazing, or he could have a psychotic split, depending on the person. There was a wonderful story of a boy named James who remembered his last lifetime as a WWII US naval pilot shot down near Japan in 1945. You can go to Youtube and type in "James" + "reincarnation", and find several videos. Here's a link to one of them YouTube - Reincarnation- past life evidence, Part 1
Weena - You're right on target, exactly. And we can even have no talent of something in this lifetime, and go into a past life and bring that talent back into this one.