Kind of feels like you can't do anything right as a parent sometimes. I'm always thinking of future DS saying to his partner in later years oh god my mum always did X, Y, Z and so on, will never do that with my own kids
He might do, I said that too about mistakes my mum made. And I haven't made them, but I have made fresh mistakes all of my very own! We're human, we learn parenting as we go along with little training, it's very hard!
My DS (5) said to me that he liked me, but he liked his dad "MUCH better". We were playing in the garden at the time, he wasn't trying to spiteful or hurtful, but he didn't realise the qualifying side to his remark would be painful for me to hear. I mean, I knew it was true, and I understood why - DH is a more fun and humorous person and generally well liked - but it really really stung hearing DS say it.
I mentioned it to him recently and at 12, he understood instantly that I would have felt hurt by it, and he said "Oh. I'm sorry Mum." At the time I had to go and sit by myself (which he didn't notice particularly, he was five and is autistic) to recover my aplomb enough to start playing again.
They say these things, and as a PP said, they can do it because they feel so secure in you that they can try to push it, and see if you'll not stop loving them. Or just not realise how acutely painful it is, like my kid.