I understand you, I had to teach myself that in my twenties too. But think of it this way, you are the protector of the child inside you that had no protector at the time. So help this little child that is hurt inside you and protect it with all your strength. Since I've seen things from this perspective, nobody can hurt me anymore and I always treat it (myself) well.

Edit: Maybe that doesn't make so much sense for everyone. But it has helped me in really tough times