Challenges in Christianity

I've proven God exists, to myself that is. A series of questions and logical conclusions have led me to this belief. It is now so engraved in my mind that, questioning the existence of God is no longer a philosophical exercise; it has become fact.

There are a few other theologies which I have accepted as fact, neither of which I care to divulge at the moment. These principles all have stemmed from the Christian theology, using the Bible as the authority. But there exist concepts which I admit to having a limited understanding of; mostly all related to the human existence.

Romantic Love. What is it? Where is its place for the Christian? (For: Examples throughout the Bible. Against: 1 Cor 7, Matt 19:1-9)

Living a Holy (Obedient) Life: Why has God commanded us not to do the very things that He knows we would do? The frustration of failing, over and over again. "Go and sin no more" John 8:1-11. Impossible. So why even make the command? Now I write this reminding myself the Saviour died because of this very predicament. But was the command made solely to judge the guilty only to show the power of redemption? What then of the Forgiven, why/how should he be expected to live without sin? (For: Rom 6-8, and others. Against: The human experience).

I am undisciplined, and my laziness prevents me from writing further.