What we know as self esteem begins, originally, in the esteem parents have for their children. Through the simplest acts of touch, attention to feelings, and guidance toward accomplishment, a child comes to see their own worth reflected in their parents eyes. When through various forms of abuse and neglect a child fails to get this mirror of love, two things happen. First the child begins to take in the feeling of defectiveness or un-loveability. A second thing also happens.
Children are masters at devising strategies to get love or prevent abandonment.
But the result will always be disappointing. Nothing can replace self love. But like anything worthwhile, it takes effort. The key is in the way we experience our memories of parenting. If our parenting was primarily supportive, our self talk will be so also.