Can a Christian choose to walk away from his or her salvation? There is a plethora of verses that say that people can not cause a saved Christian to lose his salvation, such as


  John 10:29 (NLT)   
  
  29&nbsp;for my Father has given them to me, and he is more powerful than anyone else. No one can snatch them from the Father’s hand.   


However, this does not exclude the possibility of a Christian choosing to turn away from God, as in


  Hebrews 6:4-6 (NLT)   
  
  4&nbsp;For it is impossible to bring back to repentance those who were once enlightened—those who have experienced the good things of heaven and shared in the Holy Spirit, 5&nbsp;who have tasted the goodness of the word of God and the power of the age to come— 6&nbsp;and who then turn away from God. It is impossible to bring such people back to repentance; by rejecting the Son of God, they themselves are nailing him to the cross once again and holding him up to public shame.


So, my question is: is it possible for a saved Christian to choose to walk away from Christ and thus lose their salvation?



Related:


Do parts of Hebrews 3 and 4 imply that saved Christians can become unsaved?
Once saved always saved. Is eternal security Biblical? [closed]
How does 1 John 2:19 fit with the teaching that Christians can lose their salvation


While this question is rather similar to others, I think it's focused enough to not count as a duplicate. In particular, this one is focused on the ability or inability of the Christian to choose, not so much whether losing one's salvation is possible.
This isn't a question that can be resolved indisputably here, as there are different views amont Christians about this. These views are generally in a range of:


Pelagianism - the idea that a man's salvation is an act of his free will only.
Synergysm - the idea that a man needs grace, but has to freely cooperate with it.
Irresistible grace - that grace saves even against human will.


Orthodox christians put more emphasis on free will than Roman Catholics (they are even sometimes called semi-pelagians by them). Jansenism (vide Blaise Pascal) and Calvinism share a belief in irresistible grace, while other Reformed churches vary here (somewhere between Calvin and RC doctrine).