It is clear in the Bible that we are saved by Grace through faith in Christ Jesus alone, but the confusing part is, if we are saved by grace alone through faith alone, why do we need to keep holy or doing good works to maintain(or maybe earn) salvation? Does this have the effect of making Christ’s sacrifice ineffective?   If Jesus is the only Way to Heaven, why do we need to keep doing good works (or to be holy) to go there?  Please allow me to use an example:  let’s say there’s a person who became a Christian then lived a holy life, but suddenly that person backslid and lived a wordly life. Some Christians say that person isn’t saved anymore… If that is true, does that imply that her salvation was based only on her works?  Do you believe in OSAS(Once Saved, Always Saved). If not, doesn’t create the impression that our salvation is based on your works just like the other religions?

You begin your question by stating a premise that is not biblical.   This affects my answer to your question.  We are saved by grace alone.  That is biblical.  Actually, we are saved by grace through faith (Ephesians 2:8-10 and many more), but we understand that it is the grace that saves us and the faith only activates that grace.  However, we are not saved by faith alone.  This false teaching was first given by Martin Luther, and repeated by Ulrich Zwingli, John Calvin and others in the sixteenth century.  Let me make it clear.  We are saved by faith, not by works.  In fact, no amount of work could move us even one inch toward being saved.  However, we are not saved by faith apart from works.  This is clearly taught in James 2:14-26.  This passage cannot be more clear.  James’ conclusion is that “a person is considered righteous by what they do, and not by faith alone.”  We are not saved by works, but saving faith is a kind of faith that includes works.  In fact, if there are no works, then that is 100% proof that the kind of “faith” we have is not the kind that saves us.  Our works do not save us, and our works do not make us more saved after we are saved.  But the kind of “faith” that is not combined with works is a kind which does not save.  So, we need to keep doing good works.  This is why the need to obey and to do good works is emphasized in connection with salvation again and again in the New Testament.  Look at Hebrews Ch 3-4!  There are literally hundreds of passages on this topic.  Our good deeds do not keep us saved, but if we do not continue in good deeds, then we also do not continue in faith.  Please look very carefully at Hebrews 10:36-39 and Hebrews 12:14-17.  This faith-only doctrine is not only false, it is dangerous.  It certainly has led to you being confused when you read the New Testament.  Remember, works do not save, but workless “faith” is not the kind of faith that saves.

Of course, I do not believe in “once saved, always saved.”  There are literally hundreds of warnings against falling away in the New Testament.  That is the subject of Hebrews.  Look at Hebrews 6:4-8.  But it is not just Hebrews.  What about Galatians 5:2-4 and literally dozens more.  It is utterly false to associate rejecting once saved always saved with works salvation.  God cannot be mocked (Galatians 6:7-9).  Once saved always saved sounds really spiritual, but it is not biblical.  We lose our salvation, not because we do not do enough works, but because we lose saving faith and because we willfully continue in sin (Hebrews 10:26-31).  Does Hebrews 10:26-31 teach works salvation?  I will let you decide for yourself.  Here are some more resources:    https://evidenceforchristianity.org/hebrews-lessons-in-bakersfield/   I have published a book on Hebrews:  Hebrews: Living by Faith at www.ipibooks.com