It depends on how you fail. If you fail due to natural human weakness, yes, you can repent again. But if you fail out of a willful and outright defiance of the will of God, that cannot be so easily repented of or forgiven.
Also, to repent means to stop sinning. Repenting and sinning, and repenting and sinning, and repenting and sinning, ... means that you had never repented in the first place. If you shoplift today, and repent of it tomorrow; and do it again the following day, and repent of it the next day; and do it again the following day, ... that means that you had never repented in the first place. You cannot deceive God. God knows what is in people’s hearts, and judges them accordingly.
I'm so glad that my Savior can be trusted to save me. No works ever will.
Perseverance of the Saints from the scriptures.
Every good gift and every perfect gift is from above, and cometh down from the Father of lights, with whom is no variableness, neither shadow of turning (James 1:17).
But, God commendeth his love toward us, in that, while we were yet sinners, Christ died for us. Much more then, being now justified by his blood, we shall be saved from wrath through him. For if, when we were enemies, we were reconciled to God by the death of his Son, much more, being reconciled, we shall be saved by his life (Romans 5:8-10).
And, this is the promise that He hath promised us, even eternal life (1 John 2:25).
And, for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance (Hebrews 9:15).
“Verily, verily, I say unto you, he that believeth on me hath everlasting life” (John 6:47).
“Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life” (John 5:24).
“Then shall he answer them, saying, Verily I say unto you, Inasmuch as ye did it not to one of the least of these, ye did it not to me. And these shall go away into everlasting punishment: but the righteous into life eternal” (Matthew 25:45-46).
That whosoever believeth in him should not perish, but have eternal life. For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life (John 3:15-16).
Then said Jesus unto the twelve, “Will ye also go away?” Then Simon Peter answered him, “Lord, to whom shall we go? Thou hast the words of eternal life” (John 6:67-68).
These words spake Jesus, and lifted up his eyes to heaven, and said, “Father, the hour is come; glorify thy Son, that thy Son also may glorify thee: As thou hast given him power over all flesh, that he should give eternal life to as many as thou hast given him. And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent” (John 17:1-3).
Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation m received by tradition from your fathers; But with the precious blood of Christ, as of a lamb without blemish and without spot: Who verily was foreordained before the foundation of the world, but was manifest in these last times for you, who by him do believe in God, that raised him up from the dead, and gave him glory; that your faith and hope might be in God (1 Peter 1:18-21).
I know that, whatsoever God doeth, it shall be forever; nothing can be put to it, nor anything taken from it: and God doeth it, that men should fear before him. That which hath been is now; and that which is to be hath already been; and God requireth that which is past (Ecclesiastes 3:14-15).
And we know that all things work together for good to them that love God, to them who are the called according to his purpose (Romans 8:28).
“For the Son of man is come to save that which was lost. How think ye? If a man have a hundred sheep, and one of them be gone astray, doth he not leave the ninety and nine, and goeth into the mountains, and seeketh that which is gone astray? And, if so be that he find it, verily I say unto you, he rejoiceth more of that sheep, than of the ninety and nine which went not astray. Even so it is not the will of your Father which is in heaven, that one of these little ones should perish” (Matthew 18:11-14).
“My sheep hear my voice, and I know them, and they follow me: And, I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of my hand. My Father, which gave them me, is greater than all; and no man is able to pluck them out of my Father’s hand. I and my Father are one” (John 10:27-30).
“And, this is the Father’s will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day” (John 6:39).
“While I was with them in the world, I kept them in thy name: those that thou gavest me I have kept, and none of them is lost, but the son of perdition [Judas]; that the scripture might be fulfilled” (John 17:12).
We know that whosoever is born of God sinneth not; but he that is begotten of God keepeth himself, and that wicked one toucheth him not (1 John 5:18).
“But, if I with the finger of God cast out devils, no doubt the kingdom of God is come upon you. When a strong man armed keepeth his palace, his goods are in peace: But, when a stronger than he shall come upon him, and overcome him, he taketh from him all his armour wherein he trusted, and divideth his spoils” (Luke 11:20-22).
Ye are of God, little children, and have overcome them: because greater is he that in you, than he that is in the world
(1 John 4:4).
There hath no temptation taken you but such as is common to man: but God is faithful, who will not suffer you to be tempted above that ye are able; but will with the temptation also make a way to escape, that ye may be able to bear it (1 Corinthians 10:13).
“For there shall arise false Christs, and false prophets, and shall show great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect” (Matthew 24:24).
They went out from us, but they were not of us: for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us (1 John 2:19).
Grace be unto you, and peace, from God our Father, and from the Lord Jesus Christ. I thank my God upon every remembrance of you, Always in every prayer of mine for you all making request with joy, For your fellowship in the gospel from the first day until now; Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ (Philippians 1:2-6).
And, the Lord shall deliver me from every evil work, and will preserve me unto his heavenly kingdom: to whom be glory forever and ever. Amen (2 Timothy 4:18).
Now unto him that is able to keep you from falling, and to present you faultless before the presence of his glory with exceeding joy, to the only wise God our Savior, be glory and majesty, dominion and power, both now and ever. Amen (Jude 24-25).
The steps of a good man are ordered by the LORD ; and he delighteth in his way. Though he fall, he shall not be utterly cast down: for the Lord upholdeth him with his hand. I have been young, and now am old; yet have I not seen the righteous forsaken, nor his seed begging bread. He is ever merciful, and lendeth; and his seed is blessed (Psalm 37:23-26).
And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ. Faithful is he that calleth you, who also will do it (1 Thessalonians 5:23-24).