The fact that we may not remember our former lives does not mean that we did not exist before. We do not remember the nine months of are embryonic existence in this life nor do we remember when we were 6 months old. It is all the less likely therefore that we would remember when we had lived in a different body with a different brain and nervous system and of different appearance.
It is well that we do not remember our hard experiences in the school of past lives, we might be discouraged at the prospect of having to struggle with them again we might even feel disinclined to be good again, imagining good deeds to be of no value or we might be bored by repetition. Who would care to live over again all the prankster childhood the comedies of youth the tragedies of old age or even if even one lifetime. Think what a blessing reincarnation is. It demolishes our rickety old body car and gives us a brand new model in which to try again to win the race of life.
It requires years of concentrated mental investigation to know one's former incarnations. You can know about reincarnation not by reading books or hearing lectures but through scientific metaphysical research. Reincarnation is the only logical solution to the mystery of the purpose of our lives. We are immortal souls destined to return one day to our home in God. If we die in the consciousness of mortal imperfection we cannot immediately go back to God. We must eradicate our acquired egotistic imperfections by right living. To re-establish our sole perfection may require many lives~Paramahansa Yogananda