I'd love to pick up on one of your past lives, but cannot at present, I'm still developing as a psychic.
Main lessons for reincarnation or placed back on earth, is to develop spiritualy.
Once your soul is at a certain spiritual level, or the Boss upstairs thinks that's enough time on earth, you can be taken anytime.... whether your a child, teen or adult, he will take you for the good of mankind.
Your usualy taken for the following reasons; to help someone else develop on earth by becoming their spirit guide, and the grief that you leave on earth is also a developing tool for your loved ones.
While you're a spirit guide etc, your job is to help guide and develop the person your assigned to, and at the same time, you are also developing and slowly stepping up in the spiritual world.
Hope I have enlightened you