The parable of the Pharisee and the tax collector goes several layers deep. On the surface, the conclusion is not only obvious, but is quite explicitly stated: "everyone who exalts himself will be humbled, and he who humbles himself will be exalted." (Luke 18:14). But in order to fully understand the parable, we can actually remove that "and".
See, the parable draws a contrast between these two men, but these two men exist independently of each other. The humble tax collector was humble regardless of the Pharisee. The Pharisee is irrelevant to his character. He was justified not because the Pharisee had exalted himself, but because the tax collector had humbled himself, recognising his sin before God, and begging for mercy in genuine repentance.
The Pharisee is a little different. Though the tax collector is not irrelevant to him, the sin would remain the same if a different person was involved. The sin is not exalting yourself against a humble person, but exalting yourself at all. The other person in the parable could have been a second Pharisee, the result would just be that both go down to their house without receiving forgiveness.
It is essential for us as Christians to understand the position we are in. No amount of good works can make up for sin. James even tells us that to keep the whole law and offend just one time makes us guilty of all (James 2:10). If God's standard is perfection, and you are not perfect, who are you to brag about your own goodness? As I wrote in one article, you may not be Hitler, but you aren't Jesus either.
Let us therefore cut out the tax collector completely, in order that we may become him. Do not approach the alter, do not look up to Heaven, beat your chest, and pray "Lord, have mercy on me, a sinner", for a sinner you are, and only by acknowledging that problem can you begin to solve it.
[Disclaimer: While proofreading the article, I realise the language I used may sound like I am advocating altering scripture. This is absolutely not my intention. The scripture itself is obviously flawless. I am merely talking about a way to think about it in order that we may apply it better.]