I hear you. I think about it sometimes, but I also remember that Bad Things could happen at any time, to anyone - they could die at 16 in an accident; or get cancer as a child; or even in middle age. My daughter was sorta touch-and-go with life when she was first born, and even up until 1 year we weren't sure about her heart. Accidents, misfortunes, illnesses happen, tragically. I don't think there is much reason to horrible things happening or a plan (personally) based on my own experiences, but that we should treasure each moment as it comes, because it may never be as wonderful as it is now. It helps with having a little more compassion and love for those you care about.
I think it may help you to also read all the stories and feel the love where things go well, the sun rises, the child breathes, the mama feels strong and healthy.