Our essential nature is who we are when we experience ourselves free from the influence of the past and, thus free from the influence of our personality (ego). When we come to this world, living our first years as babies, we are true to our selves, but we lack self-reflection to realize it, as it comes later with ego formation.
Thereby, by the time we become adults we aren't even aware of our true essence loss, due to the fact, that we experienced it unconsciously.
There is a solution to the problem. We can reconnect with our inner essence, by letting go of our ego manifestations, this loss will lead to growth.