The questioner has quoted:
“For You formed my inward parts; You wove me in my mother’s womb. I will give thanks to You, for I am fearfully and wonderfully made; Wonderful are Your works, And my soul knows it very well. My frame was not hidden from You. When I was made in secret. And skillfully wrought in the depths of the earth; Your eyes have seen my unformed substance; And in Your book were all written The days that were ordained for me, When as yet there was not one of them.” -Psalm 139:13-16
From this quotation above it is clear that God knew the author of the Psalm (and presumably many others too) before he was born, and God’s hand was upon him. The hand of God will be always on us all our life, whether for good or bad, depending on our choice:
Dan 12:2 And many of those who sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.
When we were born we do not automatically have an entitlement to eternal life. This only comes when we respond to God’s call:
Rev 3:20 Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me.
God will not leave us, but we can still leave God.
A related question has been answered on this site before: