I will only briefly comment on this beautiful Psalm (because I could go for hours, praised be the Lord)
verse 1: "I will sing of mercy and judgment" - if there is no sin, no judgment, there is also no mercy - but majority of people likes to sing only about mercy, which is not... let's say, it is not smart :)
"unto thee, O LORD, will I sing" Psalms are sung unto LORD, for his pleasure and not unto people and their pleasure (nor for money)... When you sing unto the LORD, you nevertheless receive much, much pleasure, but our pleasure is not the ultimate goal...
verse 2: "I will behave myself wisely in a perfect way." Who can say such a thing? Well, David did and Jesus did and everyone, who is his... Well, that is our wish and not proclamation. We ask and cry to the LORD, that we might behave wisely in a perfect way...
And the world? Well, the more sinful - the better, the stupider - the better...
"O when wilt thou come unto me?" That is a cry, Christians hanker to see the LORD, to be with him - that is the meaning of the life: to see, to know, to serve the greatest person of them all - our creator.
And the world? Well, for the world the meaning of life is whatever you want... Millions of people hanker to see, to know and to "serve" some ordinary human being or so called "holy" man - an idol... even a dead thing! and they don't care about the truth, the life, the love, the greatest person of them all...
"I will walk within my house with a perfect heart." David wrote that, that is true, but this applies also to Jesus, about whom Paul writes in his letter to Hebrews:
Heb 3:5 And Moses verily was faithful in all his house, as a servant, for a testimony of those things which were to be spoken after;
Heb 3:6 But Christ as a son over his own house; whose house are we, if we hold fast the confidence and the rejoicing of the hope firm unto the end.
Jesus did behave himself wisely in a perfect way in his own house :)
verse 4: "I will not know a wicked person." And what did Jesus say? In Matthew we read:
Mat 7:23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
verse 5: "him that hath an high look and a proud heart will not I suffer."
In James 4:6 we read: "...God resisteth the proud..." and in 1Peter 5:5 the same thing: "...for God resisteth the proud..." and in many other places...
verse 6: "Mine eyes shall be upon the faithful of the land, that they may dwell with me: he that walketh in a perfect way, he shall serve me." In Revelation 2:10 Jesus says: "...be thou faithful unto death, and I will give thee a crown of life." And in Revelation 12:11 we read: "And they overcame him by the blood of the Lamb, and by the word of their testimony; and they loved not their lives unto the death." They overcame the accuser, who is very likely Satan. And in Revelation 22:3, in the final chapter of the Bible, it is written: "And there shall be no more curse: but the throne of God and of the Lamb shall be in it; and his servants shall serve him:"
verse 8: "I will early destroy all the wicked of the land" Well, that is also written in the Revelation. He will destroy all the wicked.
"that I may cut off all wicked doers from the city of the LORD." This sentence, together with verse 7: "...he that telleth lies shall not tarry in my sight." reminds me of the following verses in Revelation:
Rev 22:14 Blessed are they that do his commandments, that they may have right to the tree of life, and may enter in through the gates into the city.
Rev 22:15 For without are dogs, and sorcerers, and whoremongers, and murderers, and idolaters, and whosoever loveth and maketh a lie.
What is this city? From Revelation 21:2 we find out, that the city is: "the holy city, new Jerusalem, coming down from God out of heaven, prepared as a bride adorned for her husband."
Bible is so great - everything makes sense :) And if your life doesn't make sense and you are cursed - well, turn to the word of God, the Bible, search for the holy city, new Jerusalem - there shall be no more curse :) and your life will make sense and you will be blessed.