Boundaries by age three
Boundary construction is most evident in three-year-olds. By this time, they should have mastered the following tasks:
1) The ability to be emotionally attached to others, yet without giving up a sense of self and one’s freedom to be apart.
2) The ability to say appropriate no’s to others without fear of loss of love.
3) The ability to take appropriate no’s from others without withdrawing emotionally.
Cloud, Henry; Cloud, Henry; Townsend, John; Townsend, John (2008-09-09). Boundaries: When To Say Yes, How to Say No (pp. 72-73). Zondervan. Kindle Edition.