Caption:
World has enough resources & place to build your castle.
Justification:
Like we see in the picture, each kid has enough sand and place to build whatever they wish to. Likewise, this world has enough resources in terms of opportunities, well wishers, family etc which can help you achieve your dreams. The level of hard-work and dedication you put to build your castle decides the beauty of your castle. Likewise your life will be beautiful as your dedication and hard-work increases. We see one girl looking at other girls, it can be perceived as if you do not wish to take efforts, the only thing you can do is enjoy someone else's dreams being fulfilled. Also once you are gone from this world, you will be known only by the dreams you achieved, the forts you conquered and the empire you built.