I am terrified to have children.

I want to have kids so extremely bad but I'm terrified that I won't be a good mother. I come from troubled parents, my mother was an addict and my Dad was on the road 90% of the time and was rarely in my life up until my late teens (18 and 19) so I didn't get much affection and it took a toll on me as a child. I just want to teach my children and love them with all of my being but I'm scared that I won't be able to live up to my own expectations. I want to educate them and just want to teach them to be good people and be happy but I'm just nervous I will let them down like I was let down. How do I overcome this fear and does anyone have any advice or has had the same thoughts as I have?