If I could see my sanctification with 20/20 vision I would have no trouble believing in my future glorification with 100% certainty. But, the fact is, I can't and I don't see my personal holiness and growth in Christlikeness with this kind of 20/20 clarity. Truth be known, most of the time I can't see it at all and this sometimes causes me to doubt my salvation. And this is serious business because if my doubts prove true and I am not a believer I have no expectation of future glorification but rather condemnation. But, what if I were tell you that God's purpose for your doubts is to give you assurance of your salvation?
You see, this inability to see our growing sanctification with perfect 20/20 vision causing us to doubt we possess it is the very thing that fuels an intense desire to be growing in Christ and holiness so as to prove the reality of our salvation. If you could see with perfect clarity your growth in Christ and holiness so as to never doubt it you would have no reason to hope for it. But, when we cannot see our sanctification clearly--resulting in us intensely desiring, crying out to God, and hoping for it we are seeing the genuineness of our faith. You see, it is the desire for spiritual growth and holiness (aka: sanctification) that gives us assurance of our salvation, continuing sanctification, and future glorification.
The Apostle Paul alludes to this in Romans 8:23-25 when he makes the point that true believers eagerly look forward to the final redemption of our bodies which finally and forever frees us from the presence of sin which fights us at every turn in our battle for holiness. He goes on to state in verse 24 that "in hope we have been saved but hope that is seen is not hope; for who hopes for what he already sees?" In other words, if you could see your progress in sanctification with 20/20 clarity you would have no reason to hope for it. Then in verse 25 he makes the all-important point that ". . . if we hope for what we do not see, with perseverance we wait eagerly for it." What Paul is saying is that our inability to see perfectly our own sanctification is the very thing that drives us to intensely desire it and persevere in waiting for it which, in turn is the assurance or proof that we are truly saved and will be glorified.
Keep in mind, unbelievers are not at all bothered by an inability to see spiritual growth and holiness let alone Christlikeness in their lives. It is not a problem for them because it simply does not interest them. Only believers care about sanctification. Only believers care about not seeing it in their lives as they think they should. Only believers desire it. So, if you are hoping for the sanctification and holiness that you cannot see very clearly if at all today--rejoice. Rejoice that you are desiring and hoping for that which only true believers in Christ Jesus desire and hope for. Rejoice that God is using even your doubts to assure you of your salvation.