As to ‘Certainty of Salvation'... there remains the awkward fact of self-deception.
C.f. Ps 19 (18): 12... 'But who can discern his errors? Clear thou me from hidden faults.’ (RSV). Not to mention the apparent surprise of the reprobate:
Mt 25: 31-46. 'Lord, when did we see thee hungry... and did not minister to Thee?' And
Mt 7:22 'Lord, Lord, did we not prophesy in your name, ...and do many mighty works in your name? And then will I declare to them, 'I never knew you: depart from Me, you evildoers'.
It is thus clear from Scripture that a simple subjective certainty of Salvation is insufficient:
‘If you love Me, you will keep My Commandments.’ (Jn 14:15).
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I might add here that KJV does not translate this accurately, when it reads, ‘If you love me, keep my commandments’. does this not attempt to put the ‘love’ first, and the ‘keeping’ as consequential? A *result* of love? Whereas the Greek word is ‘térésete’. ‘You will keep’. The keeping of the commandments is a presupposition, without which the claim to Love Him becomes meaningless.
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Thus we need to check our actual behaviour if we wish to know that we are pleasing to God. In Catholic thought it is the Sin of Presumption to believe we are saved when we are neglecting the conditions for Salvation that He has specified. And we are not authorised to dangle the bait of ‘Certainty of Salvation now’.