Can you lose your salvation?

     This chat developed out of a conversation with a pastor regarding basic Christian theology.  We ended up talking about whether or not you can lose your salvation.  Let's pick it up well into the talk.

Matt: Can we lose our salvation?
Sam: I believe we can
Matt: What must you do to keep it then?
Sam: Believe.
Matt: Phil. 1:29 says that God grants that we believe.  John 1:12 we are born again NOT of our own wills.  John 6:28-29 our believing is God's work.  So... it is up to God then, it would seem.
Sam: That is true and Hebrews say that if we willing sin after knowing the truth we no longer have an intercessor in heaven
Matt: Have you ever sinned willfully after being a Christian? 
Sam: I am not speaking of one sin, I am speaking of turning away from God.
Matt: That isn't what Heb. 10:26 says.  But, if you can lose your salvation, then what do you do with John 10:28 where Jesus says he gives eternal life and the sheep will NEVER perish?  And also 1 John 2:19, "They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, in order that it might be shown that they all are not of us." You are teaching that we keep our salvation by works.
Sam: What about those who endure to the end will be saved
Matt: That is Matt. 24:13.  That is speaking of the end times tribulation era... not of justification.  If you can lose your salvation, then what do you do with John 10:28 where Jesus says He gives eternal life and the sheep will NEVER perish?  If you can lose it then Jesus should have said, "and they may perish..." or "they CAN perish."  But he said, THEY WILL NEVER PERISH.  So, will they never perish? Or can they?
Sam: Believing is a present tense word and you must believe till the end
Matt: Yes. But can you answer the questions above?
Sam: And belief requires a response
Matt: Can you answer the question regarding John 10:28?
Sam: I believe we are God's sheep if we follow him.
Matt: Wrong.  We follow him BECAUSE we are His sheep.  You have it wrong.  This is a common error in Christianity in America.  It amounts to salvation by works.
Sam: He says his sheep know his voice and follow
Matt: Yes...and they will NEVER PERISH, right?
Sam: There are 2 schools of thought on this subject and I am not Calvinistic. But I do not want to argue about it
Matt: You don't have to be calvinistic.  Jesus said they will never perish.  1 John 2:19 says, "They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, in order that it might be shown that they all are not of us."  If someone leaves the faith it is because they never were saved.   We endure because we ARE saved...we don't become or stay saved by our works.
Sam: So you are saying that if someone accepts Jesus as his savior and feels the need to repent and follows Jesus for many years and then for some reason he turns a walks in darkness that in the end he is still forgiven.
Matt: I didn't say that.  The Bible says in 1 John 2:19, "They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, in order that it might be shown that they all are not of us."
Sam: You are saying it is impossible for a true christen to turn
Matt: To turn???  Not sure what you mean.
Sam: Away form God, to reject him
Matt: No, a true Christian cannot. Here is why. 2 Cor. 5:17, "Therefore if any man is in Christ, he is a new creature; the old things passed away; behold, new things have come."
Sam: I am saying that when we believe that we are justified and from that point on we walk with Jesus in belief and we walk each day we pick up our cross and continue walking with him
If we stop walking and turn from God and no longer trust in him as our savior then we will not enter heaven.
Matt: Right... because...1 John 2:19, "They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, in order that it might be shown that they all are not of us."  THEY WOULD HAVE REMAINED if they were really Christians to begin with.
Matt:  Now a question for you.  Are you saying that the Spirit begins the work of salvation in us and that we work it out and complete it by remaining faithful?  That IS what you are saying, that we get saved and keep it by the effort of our works, right?  Check this out. Gal. 3:1-3, "You foolish Galatians, who has bewitched you, before whose eyes Jesus Christ was publicly portrayed as crucified? ² This is the only thing I want to find out from you: did you receive the Spirit by the works of the Law, or by hearing with faith? ³ Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh?"
Sam: I would say that there are very few people who ever have lived that can say they did
Matt: You still have not answered John 10:28.
Sam: Your teaching is a new teaching
Matt: No.  Jesus taught it.  He said those with eternal life will NEVER PERISH.  John 10:28, "and I give eternal life to them, and they shall never perish; and no one shall snatch them out of My hand."  Well, will they perish or not? Jesus says those with eternal life will NEVER perish. I believe Him.  Do you?

    He stopped responding after this last statement.
    I believe that a Christian can hold the position that you can lose your salvation.  My only concern is that they do not fall into the error of trying to keep their salvation by their own works.  This is very problematic since it moves away from salvation by grace.