If our value was based on size, we would be of hardly any worth at all compared to the sun, moon, and stars. But God has made us in His image and chosen to rescue us from our sin and restore our relationship with Him. This is what gives us worth.
How is our life like a tree? As the root goes deeper, so fruit grows upward. Likewise, as Christ as declared us righteous, we begin to bear his fruit outwardly.