I'm Mormon
I won't pretend to know what it means exactly (I'm still searching for the path) but in my reflections I see the path as something the disciple would only ever see a little at a time. I see him consulting with his Lord on a daily basis. I see him having a quiet spirit so he can always here what his Lord would have him do. He runs to his God whenever he sees sin at the door as a child runs to his father when he is in danger.
There is a verse in the Book of Mormon which captures my interest every time I read it. In Alma 13:
12 Now they, after being sanctified by the Holy Ghost, having their garments made white, being pure and spotless before God, could not look upon sin save it were with abhorrence; and there were many, exceedingly great many, who were made pure and entered into the rest of the Lord their God.
I imagine God is like this. And I imagine this is what he wishes we should become
Do not forget that the pharisees were not righteous. Nitpicking over rules and being merciless and unloving is being very far from perfection. Jesus said the pharisees put burdens on people back they were not willing to lift with their little finger. He said the pharisees say but do not do. Clearly the pharisees were anything but righteous.
And you're perfectly right: perfection is a very high standard and it is impossible for man to do it. "But with God, nothing shall be impossible".
I would like to explain something about human nature that will help you understand why I don't believe in the "once saved always saved" doctrine.
I believe God grants to man according to the desires of his heart. All who want to be saved will be saved and those who do not want to be saved will not be saved. But now we come to the question of wanting: how do you determine what a person wants?
There have been moments in my life when I've wanted to be a soldier (as I'm sure is true of most boys). But did I really
want to be a soldier? Of course not. Sure I loved the glamour I thought was involved. I loved how cool it would be to carry big guns and be a hero. But did I really want to put my life in danger and be far from home for months at a time? No. So human desire is a very complex science. What someone wants today is not necessarily what they'll want tomorrow. In fact, human desire is so complex humans themselves don't usually know what they want. This is why someone can be christian today, muslim tomorrow and atheist the day thereafter. So how can you judge what some really wants? This question is extremely important especially as it regards our eternal fate.
Jesus gave a parable to illustrate how God decides. It is found in Luke 18:
1 And he spake a parable unto them to this end, that men ought always to pray, and not to faint;
2 Saying, There was in a city a judge, which feared not God, neither regarded man:
3 And there was a widow in that city; and she came unto him, saying, Avenge me of mine adversary.
4 And he would not for a while: but afterward he said within himself, Though I fear not God, nor regard man;
5 Yet because this widow troubleth me, I will avenge her, lest by her continual coming she weary me.
God requires patience and perseverance from his children. And those who persevere in the strait and narrow path show to God, the world and, perhaps most importantly, that they really want what they seek. So when I say that salvation requires something from our part it is not because I believe God is not powerful enough. It is because I believe God is a just Judge. I believe God gives us our lives here on earth mostly so we can discover and decide what we really want. And that is why the final Judgement comes only after death when we have had ample opportunity to make that decision.