If you don't believe in reincarnation, read this book. "Many lives, many master" by Brian Weiss. Our lives follow Karma, bad karma may not happen in current lives, but certainly in next lives. In fact, Dr Weiss discovered that reincarnation scriptures had been written in the original old testament of the Bible, they were just removed deliberately by the religious leaders because their powers would be weaken. This is something we need to be clear about of life, you won't go to heaven just by expiating your sins.
If you ask me why there are so many disabled peoples in the poor countries who are suffering, it is because of their bad karma from previous lives.