I have never been into a lot of the "self-concept" teaching that we encounter today. I believe concept is built on tangible evidence. It does no good to tell a child, "You are a great student!" if that child can not read. Teach the child to read, however, and the child will feel successful.
I found the greatest success tool when I worked with inner city kids was the camera. I took lots of pictures and set them on the classroom computers as slideshow screen savers. The look on the faces of the children when they saw their pictures was priceless. The picture always showed them being successful in class. The child would sit up straighter, and you could see they could now see themselves as a student, doing valued work. I think they could see themselves as likeable through the eyes of someone who liked them. That makes all the difference in perception...perspective.
How do you see yourself in God's Kingdom? Do you see yourself as a failure, of little value to the kingdom? Do you let the devil kick you around for mistakes? Positive thinking is of little value. Find something to do for God and do it. Then see how you feel. Let Satan see your true Kingdom colors. Forget the positive thinking and turn all the lights on. The companion video lesson on my Animated Faith Zone for Kids today has more on this topic @ http://www.animatedfaithzone.com/index.html