The contrast between the world we leave when we take on human form and this world we arrive in is very great. Mostly we have dealt with it by forgetting where we came from and getting on with the life we found for ourselves here on Earth.
I believe it is less easy now for children to use this strategy. Children now, not all by any means, but perhaps more than we tend to assume, are arriving here with strong, clear memories of other, expanded and naturally joyful states of consciousness. They may not be able to articulate this (or perhaps may not choose to) either to others or even to themselves, but the feelings such recollections generate can be very powerful.