"Can a Christian lose salvation?"
though many wants to believe .."once saved,always saved", that's a false teaching,in a sense. meaning Jesus dead was a gift for ALL humans,who decides to follow his Teachings,and do HIS Father's WILL,(Matt.7:21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven). when we get baptized,we are blessed with the gift of everlasting life, because of Jesus death. at that point of coming out of the water,we are sinned-free. so at that point,we have the gift of salvation.
NOW!... here's what many refuse to believe,simply because they're NOT TRUELY living the way Jesus taught us to live, and refuse to serve his Father. ONCE we do our first sin,after leaving the baptismal waters, guess what?!...we now lost that gift.
If we have lost it, why does the word tell us that Jesus is our advocate on high when we sin?
Why does He give us parables about going to find the sheep that wandered away?
Or the Father waiting for his son to return to him?
God promises that He holds us in His righteous right hand and NOTHING can snatch us from His grasp.

Not even our very own selves.
(1).Heb.10:26,27- For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, But a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.(many Christians don’t realized from about 10 minutes after coming out of the baptismal water, we might have sin,even if it was a small lie. Be-it willfully or unknowingly. Therefore we made void,what was meant to be.in other words…we’re NOT SAVED,now standing in judgement).
So the shed blood of Jesus wasn't that powerful then? If all it takes to void what He did on the cross is us goofing up and sinning...man, that's depressing!
(2).1John :9 ,10-If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness. If we say that we have not sinned, we make him a liar, and his word is not in us.
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AMEN! He forgives us because He knows us. loves us and calls us His own!
Hebrews 10:11-18
11 Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. 12 But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God, 13 and since that time he waits for his enemies to be made his footstool. 14 For by one sacrifice he has made perfect forever those who are being made holy.
15 The Holy Spirit also testifies to us about this. First he says:
16 “This is the covenant I will make with them
after that time, says the Lord.
I will put my laws in their hearts,
and I will write them on their minds.