Can you lose your salvation?

Well, in a word, yes, of course, we know this historically. During the times of persecution, there were people who denied their Christian faith in order not to be martyred. So yes, of course. This is why Christ says, if you deny me before men, I will deny you before the Father. So of course this is possible for people to leave the Christian faith, and in the process of leaving the Christian faith they leave being a testimony of Christ before the Father.