This is a very complex question and I think you could very well argue both sides and convince people for both sides, but I will try and express how I believe it. Salvation is a free GIFT that God choose to give to us, but the catch is we have to be willing to accept the gift. I don’t believe our gift of salvation is like a medal that we just receive and will always have, I believe it’s more like a plant, we have to water it and give it what it needs to be healthy and if we don’t tend to it will die and not produce fruit. Salvation is a never ending Journey that we have to fight for every day, "Work out your salvation with fear and trembling" (Philippians 2:12). So our salvation is something that we do need to work at and allow God to change and mold us, and the work in our lives will never be finished simply because we are not perfect, if we were we wouldn’t need saving. Another point to bring up is that God only judges us by what we know, so if as a Christian we sin but do not know it is a sin I believe God will not judge us on that, BUT when we knowingly sin what we are actually doing is turning our back on God and pretty much saying I don’t need to do what you tell me. I am not saying that if we sin once we lose our salvation, but rather if we willingly and knowingly, continuously sin I believe our salvation is then lost, because in doing that it is like we are throwing Gods free gift back in His face. (Ezekiel 18v13-32) Yes this is an Old Testament verse but the same basic principals apply
Some may argue that true Christians don’t ongoingly live an immoral life, and that if they do they were never really redeemed in the first place. However this is cannot be true because I did exactly that, when I was younger I loved God with all I was and was very close to Him, but as teen years hit I began to be swayed by the world and knowingly did walk away and I believe that if I had have died during that time in my life I would not have gone to heaven.
Losing your salvation is much like receiving it, is a conscious decision, the bible says that the devil is hiding at every corner seeking whom he can devour (1 Peter 5v8,), he is constantly seeking to rob us of our free gift (salvation) and convince us we don’t need saving, simply because his mission is to steal kill and destroy us (John 10v10)
Salvation is about our relationship with Christ and just like any earthly relationship we need to spend time and effort into getting to know that person, otherwise on the Day of Judgment Jesus will say sorry I don’t know you. It’s a daily choice we need to make, not just a once saved always saved kind of gift.
