Before I learned to swim I would always look for the shallow end of the pool. When it comes to the doctrine of God there is no shallow end:
His judgements are unsearchable (Rom. 11:33)
His ways are inscrutable (Rom. 11:33)
No one has known his mind (Rom. 11:34)
No one has been his counsellor (Rom. 11:34)
His greatness is unsearchable (Psalm 145:3)
His understanding is unsearchable (Isa. 40:28)
Heaven, even the highest heaven cannot contain him (1 Kings 8:27)
He inhabits eternity (Isa. 57:15)
From everlasting to everlasting he is God (Psalm 90:2)
The depths of God are searched by the Spirit, and the Spirit comprehends the thoughts of God (1 Cor. 2:10-11)
No one has seen God, God the only begotten, who is at the Father's side, has made him known (John 1:18)
The love of Christ surpasses knowledge (Ephesians 3:19)
Until and unless the weight of God's infinite being is straining your thoughts to breaking point, until and unless you have felt the finitude of your mental powers in contemplating the Father, the Son and the Holy Spirit, you have not even begun to fathom the unfathomable depths of the One, Living, True, and Triune God.
When we say that Jesus existed "pre" his incarnation, we do not mean he preceded it by any finite amount of time. The Son of God preexisted his incarnation the way that the Creator preexisted creation: infinitely.Fred Sanders, Embracing the Trinity, p. 85
Preexistence may be easy to say, but that one little syllable, pre-, is a quantum leap from Here to There, from time to eternity. Before you have finished that syllable, you have left behind everything measurable and manageable.