I think someone can lose their salvation (but I think it would be really hard to)
Luke 12:10 And everyone who speaks a word against the Son of Man will be forgiven, but anyone who blasphemes against the Holy Spirit will not be forgiven.
The key to knowing what this means is to know what blaspheming the Holy Spirit means. My understanding is that it is a willful, constant, long-term turning away from God. An imperfect example would be a someone who fully understands the Bible and continues to worship Satin for their entire life. So if someone is in relationship with the Lord and then turns away from them for the rest of their lives and never repents, this may apply to them.
Hebrews 6:4 "It is impossible for those who have once been enlightened, who have tasted the heavenly gift, who have shared in the Holy Spirit, 5 who have tasted the goodness of the word of God and the powers of the coming age 6 and who have fallen[c] away, to be brought back to repentance. To their loss they are crucifying the Son of God all over again and subjecting him to public disgrace."
This one is a little hard for me to make sense of in light of the other two. The other two speak of life through repentance, yet this says repentance is impossible to those who have fallen away. We see a contradiction of this in scripture regarding Peter. He denied Christ three times yet was brought back in the fold. So that begs the question, what is falling away? Based on God's faithfulness, mercy and patience with his people in both testaments, it makes me think it is the same as blaspheming the Holy Spirit, a point of no return where you have turned your back on God. However, I'm not 100 percent certain of this.
Luke 15:11-32 The Prodigal son
This is hard to make a theological point off of alone because it is a parable and is not speaking of heaven and hell, but of how the Father see's and treats us. The idea I have here is that the Father was instantly ready to take the son back once he saw him in the distance. Yet what would have happened if the son never came back? He would not have been reconciled to his Father. Essentially what I'm getting at here is if one is in relationship with God the Father, and leaves never to return, that is what my understanding is of blaspheming the Holy Spirit, an unforgivable sin and a falling away. Part of me thinks it's possibly unforgivable not because God is unable to forgive it, but because the person doesn't want it forgiven. If they did, they would be reconciled to God like the prodigal son was to his Father.
All in all if the story ended with the son dying while feeding pigs, he would not have been reconciled with his Father. I think the same would apply to a Christian who falls away, blasphemes the Holy Spirit and walks away from God. They have left the family and are not reconciled to the Father, thus losing their salvation.