The only way to judge one's own election is by (a) a conviction granted by testimony to the heart by the Spirit within and (b), a transformation of preferences/wants/desires especially in regards to a desire to carry out the ordinary means of grace, and (c) a heightened sensitivity to sin paired with God's discipline leading to confession and repentence. Ultimately, saints granted saving faith will persevere until the end, while those lying to themselves will fall away from Christ.

Is there no physical representation of the actions of the Holy Spirit? In this case the sacrament of penance. Has the Christ left us with only the a, b, and can to go on? Can one on Earth not lose their sanctifying grace through committing mortal sin? Or do you posit that they never had this sanctifying grace if they could choose to commit mortal sin? If this is the case, could one chosen by God to be sanctified ever choose sin?