Why couldn't we reconcile ourselves to God? I always hear people say things like, 'the debt was too large' ... well, why? Why couldn't I pay for my own sin? 

I don't like that Jesus took punishment for me, I would hate for my earthly father to get fined or beaten or imprisoned for me, it would enrage me, it's completely unfair. I want to pay the price myself. Why can't I? 

The only thing that seems to make sense is that for some reason there had to be a blood sacrfice and that sacrfice had to be a perfect being (similar to how animals could not be sacrficed if they had any defects.) ... but why? Why does the person/animal dying need to be perfect? 
It doesn't make sense to me yet, I know it's the truth because I believe in God but I feel like there's a block in my understanding, like I'm waiting for a lightbulb moment where I go 'ahhhh ok now I get it.' PLEASE DON'T SAY 'there are some things we will never understand because God is God and mysterious and we just have to deal with that.' I don't believe that is the case with such a critically important issue. The early Christians seemed to have such a good grasp on the whole concept but it's evading me. Please offer your understanding if you get it. Please don't say anything if you're not 100% sure. 

Thank you so much, I really want to get this so I can move forward in my faith.
The question, as stated, presents an misunderstood view of the economy of salvation. And although it is ultimately a mystery, we can say a fair amount about sin and salvation that makes Christ's sacrifice more reasonable sounding, and the possibility of "self-salvation" far less reasonable sounding. In essence, God created humans to be like God, humans thought they were getting short-changed and disobeyed God (His Word, the law of life), so God had to become fully human to make humans like God again.

First, God makes man in His image. We can see this directly in scripture. As creation culminates, God creates man and woman.


  God created mankind in his image; in the image of God he created them;
  male and female he created them. (Genesis 1:3)


Second, God places man and woman in the Garden of Eden, the Garden of delight. He gives them dominion over everything except the prerogative of good and evil. Based on context, this could mean divinity itself. The Catholic read on this, as I understand it, is that humanity is initially created in a state wherein they will live joyfully and forever, provided that trust in God's exclusive right to determine good versus evil and who is entitled to what.


  15 The LORD God then took the man and settled him in the garden of
  Eden, to cultivate and care for it. 16 The LORD God gave the man this
  order: You are free to eat from any of the trees of the garden 17
  except the tree of knowledge of good and evil. From that tree you
  shall not eat; when you eat from it you shall die. (Genesis 2:15-17)


Third, mankind starts to believe that God is holding out. They believe that, although they were told they were made in God's image, that they actually far from God-like. They believe that they must take matters into their own hands, and they taste the forbidden fruit.


  1 Now the snake was the most cunning of all the wild animals that the
  LORD God had made. He asked the woman, “Did God really say, ‘You shall
  not eat from any of the trees in the garden’?” 2 The woman answered
  the snake: “We may eat of the fruit of the trees in the garden; 3 it
  is only about the fruit of the tree in the middle of the garden that
  God said, ‘You shall not eat it or even touch it, or else you will
  die.’” 4 But the snake said to the woman: “You certainly will not die!
  5 God knows well that when you eat of it your eyes will be opened and
  you will be like gods, who know good and evil.” 6 The woman saw that
  the tree was good for food and pleasing to the eyes, and the tree was
  desirable for gaining wisdom. So she took some of its fruit and ate
  it; and she also gave some to her husband, who was with her, and he
  ate it. 7 Then the eyes of both of them were opened, and they knew
  that they were naked; so they sewed fig leaves together and made
  loincloths for themselves. (Genesis 3:1-7)


At this point, all humans are destined to die. People are finite and stupid, for one. And our pride destines us to die. We simply don't know what it means to be Godlike, nor do we have the power to acquire Godliness. We don't even fully understand what good and evil are, let alone the power to enact good. Least of all do we understand the full consequences of our actions, nor have the power to understand. Hence, having taken good and evil into our own hands, we cannot fulfill God's purpose for us to be like Him. We simply don't have the ability to raise ourselves to Godliness.

Fourth, God rescues mankind. And since the original plan was for humans to be like God, God can accomplish this by entering the full human experience. From birth:


  10 The angel said to them, “Do not be afraid; for behold, I proclaim
  to you good news of great joy that will be for all the people. 11 For
  today in the city of David a savior has been born for you who is
  Messiah and Lord. 12 And this will be a sign for you: you will find an
  infant wrapped in swaddling clothes and lying in a manger.” (Luke 2:10-12)


Through daily life, learning, teaching, eating, partying, friendship, betrayal, judgement, and denial to suffering, agony, mockery, and death.


  Jesus cried out in a loud voice, “Father, into your hands I commend my
  spirit”; and when he had said this he breathed his last. (Luke
  23:46)


And the Catholic understanding of this is twofold.

Firstly, we understand that Christ makes humans like God again by bringing the fullness of God into the full human experience. This is often called divinization or deification. Because Jesus was fully God, everything that He was as a human, all that happened to Him, and all that He did is God-like, including death, which we are bound to!


  The Son of God became man so that we might become God.
  - St. Athanasius


Not coincidentally, Jesus is risen from the dead, suggesting in a very "loud" manner that we too can be risen. But not of our own doing! Only by accepting God's offer for salvation by "commending our spirit" to God! That is, we can only allow ourselves to be risen by God by allowing God's offer, the power of the cross, to make us like Him again. We cannot do it on our own, for we are not God. It is precisely in an attempt to "do it on our own" that we are apart from God.

But secondly, and contrary to your request for this question, we understand that the mechanics of salvation are a mystery! It's well and good to talk about deification. It's well and good to say that Christ became sin, as we often do. It's well and good to talk about paschal sacrifices, the law, the Word Made Flesh, etc. But, that doesn't mean we understand it. And if we start to presume salvation and God are not mysterious, we find ourselves back in front of the forbidden fruit, ready to take that ill-advised bite.