"Proof of Pre birth Soul contract - Can be accessed through meditation or you could visit a good PLR (Past Life Regression) conductor who can show you how and why you selected the life that you have.

"Why we select so much pain for ourselves" - Unless we live through each experience it does not have a Soul impact. If I wish to experience kindness then I need another soul to suffer so I can be kind to it. Besides pain or pleasure is our way of looking at things...in soul perspective everything is simply an experience that you need in order to complete your Soul Journey.