Sinners can convince themselves they are saved in two main ways:
1) Change the character of God
2) Change the character of themselves
The problem with this strategy is that it won’t work, it merely makes you a liar.
If you change the character of God–pretend He is loving like you want Him to be loving–it won’t actually change God, just your take on Him.
If you change the character of you–pretend you are not as sinful as you really are–it won’t fool God because He knows your heart.
If either of these strategies is employed to give you assurance of your salvation, you may indeed experience assurance in your mind. But whether you feel assured means next to nothing.
“Yet thou sayest, Because I am innocent, surely his anger shall turn from me . . . the LORD hath rejected thy confidences, and thou shalt not prosper in them.”