You need to accept the fact that you cannot keep the law. Stop trying to be Jewish and be a Christian. "The Just Shall Live By Faith" Romans 1:17 and not by rules, laws and religion.
Actually, Paul was quoting an Israelite Prophet under the Law, there.
The narrative of which had originally been...
Habakkuk 1:1 The burden which Habakkuk the prophet did see. 1:2 O LORD, how long shall I cry, and thou wilt not hear! even cry out unto thee of violence, and thou wilt not save! 1:3 Why dost thou shew me iniquity, and cause me to behold grievance? for spoiling and violence are before me: and there are that raise up strife and contention. 1:4 Therefore
the law is slacked, and judgment doth never go forth: for the wicked doth compass about the righteous; therefore wrong judgment proceedeth. 1:5 Behold ye among the heathen, and regard, and wonder marvellously: for I will work a work in your days, which ye will not believe, though it be told you. 1:6 For, lo, I raise up the Chaldeans, that bitter and hasty nation, which shall march through the breadth of the land, to possess the dwellingplaces that are not theirs. 1:7 They are terrible and dreadful: their judgment and their dignity shall proceed of themselves.
The reason for that bit of very distressing news about what would befall his nation for their Unfaithfulness TO THEIR Law but at the same time, a reason for hope against hope nonetheless?
Habakkuk 2:1 I will stand upon my watch, and set me upon the tower, and will watch to see what he will say unto me, and what I shall answer when I am reproved. 2:2 And the LORD answered me, and said, Write the vision, and make it plain upon tables, that he may run that readeth it. 2:3 For the vision is yet for an appointed time, but at the end it shall speak, and not lie: though it tarry, wait for it; because it will surely come, it will not tarry. 2:4 Behold, his soul which is lifted up is not upright in him:
but the just shall live by his faith.
That last part in bold there would also be manifested by one such as their Prophet Daniel.
And Paul had had all that in mind, in Acts 13, also...
Acts 13:37 But he, whom God raised again, saw no corruption. 13:38 Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: 13:39 And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses. 13:40 Beware therefore, lest that come upon you, which is spoken of in the prophets; 13:41 Behold, ye despisers, and wonder, and perish: for I work a work in your days, a work which ye shall in no wise believe, though a man declare it unto you.
By the way, that right there is another example of Paul quoting the OT, not so much for what it had originally applied to, but because its basic operating principle is the same.
He also makes use of his unique aplication of it, in Romans 2 and into...
Romans 3:1 What advantage then hath the Jew? or what profit is there of circumcision? 3:2 Much every way: chiefly, because that unto them were committed the oracles of God. 3:3 For
what if some did not believe? shall their unbelief make the faith of God without effect?
And in...
Romans 9:31 But Israel, which followed after the law of righteousness, hath not attained to the law of righteousness. 9:32 Wherefore? Because
they sought it not by faith, but as it were by the works of the law. For they stumbled at that stumblingstone; 9:33 As it is written, Behold, I lay in Sion a stumblingstone and rock of offence: and whosoever believeth on him shall not be ashamed.
In other words BOTH systems revolve around the issue of the just (each within their respective system - Law or Grace) living by faith towards God within their particular "instruction in righteousness."
In Time Past, under the Law...
Deuteronomy 6:24 And the LORD commanded us to do all these statutes, to fear the LORD our God, for our good always, that he might preserve us alive, as it is at this day. 6:25 And it shall be our righteousness, if we observe to do all these commandments before the LORD our God, as he hath commanded us.
An example of which had been...
Luke 1:5 There was in the days of Herod, the king of Judaea, a certain priest named Zacharias, of the course of Abia: and his wife was of the daughters of Aaron, and her name was Elisabeth. 1:6 And they were both righteous before God, walking in all the commandments and ordinances of the Lord blameless.
And But Now, this side of Israel's fall and temporary setting aside by God in His Grace...Rom. 11:25-29.
Romans 5:20 Moreover the law entered, that the offence might abound. But where sin abounded, grace did much more abound: 5:21 That as sin hath reigned unto death, even so might grace reign through righteousness unto eternal life by Jesus Christ our Lord.
Case in point?
Acts 7:51 Ye stiffnecked and uncircumcised in heart and ears, ye do always resist the Holy Ghost: as your fathers did, so do ye. 7:52 Which of the prophets have not your fathers persecuted? and they have slain them which shewed before of the coming of the Just One; of whom ye have been now the betrayers and murderers: 7:53 Who have received the law by the disposition of angels, and have not kept it. 7:54 When they heard these things, they were cut to the heart, and they gnashed on him with their teeth.
Romans 3:19 Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. 3:20 Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.
And that knowledge right there is experiential, Acts 15; Rom. 7; etc.
3:21 BUT NOW the righteousness of God WITHOUT the law is manifested, being witnessed by the law and the prophets; 3:22 Even the righteousness of God which is by faith of Jesus Christ unto all and upon all them that believe: for there is no difference: 3:23 For all have sinned, and come short of the glory of God; 3:24 Being justified freely by his grace through the redemption that is in Christ Jesus: 3:25 Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God; 3:26 To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus.
Nevertheless, Robert, Rom. 14:5 towards you; in memory of Rom. 5:6-8 - in both our stead.