I suppose it feeds the flesh (and pride) to think we need to do something to show how sorry we are for our sin.
But God tells us to just come to Him and He will grant forgiveness, free and clear, no strings attached.
People are always suspicious of things that seem too good to be true.
But in God’s case, it is, and it is true.
Well it really falls in the lines of not having assurance of their salvation...even more that it's sinful to think that's possible...(see the trap).... You must accept the assurance Jesus claims that we have in Him or none of the rest matters....they often remain in their sins channeled through a false sense of security via the Mass and Priesthood which causes them to rely on that which they can taste touch and feel....Faith independent of such is not imaginable let alone practiced.