This is in response to your answer to the question, '' whether a friend who commited suicide is in heaven.'' I don't understand your answer. For many of us Christian suicide is a sin. No one has the right to take his/her life (Genesis 9: 4-6). But maybe I don't understand the whole thing. But my question is " can a Christian lose his/her salvation and what can make him/her lose it."
Suicide is a sin, it is the taking of a life; however, someone can commit suicide and still go to heaven because salvation is not based on behavior, it is based on the free gift of God's grace through the death of Jesus Christ.
Once we receive Christ and have our sins forgiven we are given eternal life. Eternal means forever. There is nothing we or anyone else can do to cause God to remove our salvation. Once we are saved, we are always saved
I have copied below an answer I wrote to another person that may be of help.