In Hinduism, Jainism, Sikhism and Buddhism, reincarnation is a fundamental belief. It is believed that souls take rebirth in different forms of life, according to their karma, until they attain moksha (salvation). In the next birth, you start your karma cycle from where you left off in the previous birth and you go forward from their or regress, which depends on your upbringing, environment, circumstances and simply your character. The choices you make in your lifetime decide where you will go.
Another common belief about reincarnation is that when the baby is in the womb it is connected to God the most and is hanging upside down because nature is punishing it for not fulfilling its karma in the previous birth. It asks for forgiveness and another chance to come back into the world and follow the path of righteousness and salvation.
Who has ever broken the cycle of life and attained moksh? Maybe Budha? Krishna? Rama? Who is to say? At the end of the day, religious or atheist, believer or nonbeliever, follower or leader, being human is the way of positive karma. Actually being human in its every definition is the way to go. Having the innocence of a baby, loving heart of a mother, discipline of a father, care and protective nature of a sibling, is what being human is.