While incarnated, we experience the "veil of forgetfulness" that blinds us, temporarily, to the events of our past incarnations. This is actually a blessing from God, for if we were actually able to remember such events, these memories could greatly amplify our suffering and cause a great obstacle to making any progress in the present. God allows us this gift, then, in order to give us a fair opportunity to undergo our trials and expiations with success. 

For more explanation about this temporary forgetfulness of our past, please read the similarly titled segment found in the web section "Life in the Material World" (see menu bar at left).