No way of knowing?

I took my daughters to an amusement park near our home yesterday. They each brought a friend and had a great time and as I was sitting on a bench waiting for them to come off a ride I looked over to my side there was a mom and her two little kids... a  girl about 6, and a boy about 3 and a half ,they were having ice cream and the mom was taking pictures of them pretty much a typical scene and then it hit me that 15 years ago that was me and my son and  i could never have imagined then where I am today. There was no way of knowing that my beautiful little boy would end up a heroin addict at the ripe old age of 18. I felt so cheated and robbed of every hope and dream I have ever thought of for him and today I  am very depressed.  This is just so unfair ! Why do I and all my friends on here have to carry this horrible burden I would rather have to fight a terrible illness myself then have to watch my son struggle and I am so angry. I am angry at myself for not seeing the signs of him turning down the wrong path. I'm angry at the no good piece of garbage that introduced that evil crap to my son I'm angry at my son for not having the strength to walk away and never try it to begin with. I know that none of this is fair and life isn't fair it seems all too often that terrible things happen to good people and I don't like it . I hope that mom at the amusement park never knows the pain I suffer I wouldn't wish this on anyone.