It always surprises me when I get a shocked look to this statement: "The proof you are a Christian is not some card you signed or aisle you walked - it is whether or not you are living for Jesus now, today."
Throughout the New Testament, both Jesus and His disciples make this perfectly clear. Consider Jesus' foundational parable of the four soils. One soil is hard and shows no fruit. The last soil is good and yields a large harvest. The other two soils (rocky and weedy) seemed to show some real fruit, but in the end were proven to be false. Either persecution or something like covetousness creeps in and the false professor is exposed. (See Mark 4.)
In other words, they did not persevere to the end.
In His Olivet Discourse (Mark 13), He notes the fact that "the one who endures to the end will be saved." Clearly, the one who does not endure is not saved.
Paul never spoke of his "having arrived" spiritually, even though he clearly believed in and taught God's preservation of the elect. He wrote to the Philippians, "Not that I have already obtained this or am already perfect, but I press on to make it my own, because Christ Jesus has made me his own. Brothers, I do not consider that I have made it my own. But one thing I do: forgetting what lies behind and straining forward to what lies ahead, I press on toward the goal for the prize of the upward call of God in Christ Jesus" (Philippians 3:12-14).
Here is the great Apostle, the one who similarly wrote "nothing shall separate us from the love of Christ," being careful not to predict his own future - rather entrusting it to God. ("Let those of us who are mature think this way, and if in anything you think otherwise, God will reveal that also to you. Only let us hold true to what we have attained" :15-16).
Other examples could be cited, but I think it is important to ask the question, "Where do I stand with the Lord today?" This is not meant to excite doubt, but to promote a focus (better, faith) on Christ! The fact is, I am nowhere today apart from Jesus. My salvation rests as squarely on His shoulders today as it did that first moment I breathed out words of repentance and faith.
I would suggest that part of the reason evangelicalism is in such an odd condition is this sin of presumption when it comes to our standing before God. I do not doubt my salvation (praise the Lord!) one bit. The Lord has blessed me with great assurance most of my adult Christian life. But my assurance is not what saves me. Christ is my Saviour. And the moment I begin to focus on my actions, feelings, or past decisions, I have declared allegiance to a new christ.
So, I suppose I am suggesting two things. 1. We need to ask ourselves where our hope for heaven lies. Is it in Christ alone? 2. Is there evidence in my life of this living for Jesus? Beyond a rational and logical, positive answer to question one, we need to move to testing for the fruit which always accompanies such a genuine positive answer. Do I really, truly, genuinely and in recent history exhibit behaviours that "adorn the Gospel?"
Two questions worth asking our souls often - and without fear! For a negative answer to either only points us back to the one solution to both -- Jesus!