Just one child

I can't stand when people without children of their own try to give parenting advice or make statements about how THEY would parent or judge how others parent. I think most parents feel this way, and it's not really a secret. But what is new for me is feeling this way toward people with only one child. It's not nearly as strong of a feeling as the ones I have toward non-parents but I can't help but be a little annoyed when a parent with one kid tries to tell me that "this is how to do it" or "I did it this way and it worked for me" or "I do this and my kid has turned out okay" etc etc.....
I understand why they feel this way, because I actually felt this way a little bit with my first. I wanted to take a little bit of credit for everything she did. She walked early, she was an advanced talker and relatively smart for her age. She slept through the night in her own bed at three months old. She was easily and quickly potty trained at just 22 months old. Of course, I wanted to think that all of this had to be from my parenting skills. I'll admit- I especially felt this way about the potty training. I thought that I knew the right method and thought that if everyone just listened to me, potty training wouldn't be a big deal.
Until I had two more kids and tried the same method. It didn't work with either of them. Eventually I had my girl twin trained around 26 months but at almost 2 1/2 I'm still battling with my son. I've decided that there is no right way to potty train. You have to know your kids personality and do what you think will work for them.
I'm learning to eat my words on a lot of things. A lot of things that I said I would NEVER do.... use pull ups for example. I was strongly against them and now I'm not. The daycare actually requested them so they could  work on potty training as a class without cleaning up the accidents of 16 two year olds. I get it now. Maybe for a kid who's not in daycare, pull ups seem silly but with my kids and our situation it works.
Until you have more than one kid, you aren't able to see just how much each child comes into this world with their own personality and that you really have to tweak your parenting for each child.
Parents of one kid- don't take too much credit for anything.