Lest anyone should fall

It seemed to me that the only way I could know I was saved was by knowing the status of my eternal election. Was I chosen by God for salvation or was I eternally damned before I had done anything good or bad? To be sure, the Calvinist theologian in me had responses to this question, yet none of them sufficed…my Calvinistic theology presented my needs for assurance with an epistemological problem: in order to have assurance I needed to know the status of my election, something that by definition is secret and cannot be known. 

https://ochuk.wordpress.com/2008/03/27/why-i-am-not-a-calvinist/

That's illogical:

i) Calvinist Christians can know they are saved in the same way that Arminian Christians can know they are saved: by believing the Gospel.

If it be objected that a professing Christian can be self-deluded, that's possible for Calvinists and Arminians alike.

ii) In addition, it's demonstrably false that God's secret decree is by definition unknowable. For instance, past events are part of God's secret decree, but once they eventuate they are knowable. 

This objection was articulated in an article by William Lane Craig entitled “Lest Anyone Should Fall”: A Middle Knowledge Perspective on Perseverance and Apostolic Warnings where he essentially argues that the “means of salvation view” is actually more coherent in a “middle knowledge” perspective. Middle knowledge is the view of God’s knowledge that contains what his creatures would freely do in any given circumstances (or “possible world”) before he creates the world. This contrasts with the Calvinist perspective in that it allows for libertarian free will, which is a view of freedom that is incompatible with causal determinism…As far as I can tell Craig is able to make sense of the real possibility of falling away and the means necessary for guarding against it via God’s middle knowledge, which Calvinism cannot.

And what does Craig say:

The Molinist who holds to the perseverance of the saints may regard (4) and (4') as false because, in counterdistinction to the Congruist, he holds that there are realizable worlds in which believers do reject God's grace and apostasize. That is to say, such worlds are not merely logically possible, but are feasible for God. But the Molinist who holds to perseverance will simply add that God would not decree to actualize any of these worlds, or even more modestly, that God did not in fact decree to actualize such a world. In the world He chose to actualize, believers always persevere in the faith. Perhaps the warnings in Scripture are the means by which God weakly actualizes their perseverance. That is to say, in the moment logically prior to creation, God via His middle knowledge knew who would freely receive Christ as Savior and what sorts of warnings against apostasy would be extrinsically efficacious in keeping them from falling away. Therefore, He decreed to create only those persons to be saved who He knew would freely respond to His warnings and thus persevere, and He simultaneously decreed to provide such warnings. On this account the believer will certainly persevere and yet he does so freely, taking seriously the warnings God has given him.
Of course, Molinism does not imply the doctrine of the perseverance of the saints. The defender of middle knowledge could hold that logically prior to creation God knew that there were no worlds feasible for Him in which all believers persevere or that, if there were, such worlds had overriding deficiencies in other respects. Therefore, the warnings of Scripture do not guarantee the perseverance of believers, for believers can and do ignore them.
http://www.leaderu.com/offices/billcraig/docs/lest.html

To play along with Adam's objection, this generates a parallel epistemological problem for assurance: in order to have assurance he needs to know his modal status. Is the actual world in which he exists one of the possible worlds in which he'd persevere–in contrast to other possible worlds in which he'd lose his salvation?? Which possible world did God instantiate? One in which he finishes the race or one in which he drops out of the race before the finish line?