A juvenile reaches that stage in life when it is time to take leave of mom and dad and face the world.

Notes:
The situation can be featured from either the child's or a parent's point of view. Children may find it hard to leave, or parents may find it hard to let them.

Examples:
Wesley wrestled with leaving the comfortable confines of the Enterprise-D to enter Starfleet Academy in tng3x24 "Ménage à Troi".

References:
https://en.wikipedia.org/wiki/Leaving_the_nest