Why cant parenting come with instructions!!

I always felt like I was doing things right for my boys but then as they get older I feel like everything I'm doing is wrong I hate making them cry but I also hate when they don't listen weres the correct answer on what to do !!! Being a parent is probly the hardest thing in the world all I can hope is my boys will love me no matter what .....random thought just had to get it out a my head ...no one ever said being a mother was easy but sometimes I'd like to have a future look on things to know what I'm getting myself into