I think it can be possible for adults to learn to love themselves. After all, I think the act of calling kids awful is to make them do what you want. However, they grow up and obtain freedom eventually, and what situation they are in can probably change these thoughts over time. Such as, if they are in a healthy environment.

However, for me personally, it feels like rebuilding yourself from the inside sometimes. One milestone can lead to another sore spot that has to be grown over with kind words and understanding towards myself. Sometimes I don't even liked to be valued because I had been taught I was valueless, and so get anxious that people will lose their hopes about me at some later time. It's about not being taught I was unconditionally valuable. I'm sure a lot of people feel this way, and I don't think it's a healthy way of thinking.

Like they say, you become what you are called. I don't think this is entirely true... But I think it is to some extent.