The power of Christian repentance is unbounded.
If we sin, we should repent. If we cannot undertake not to commit that sin again, then we should repent that failure too (double-repentance).
If we sin, and we cannot resolve not to commit that sin again, and we cannot even find the resolution to want not-to commit that sin again - then we should repent that failure too (triple-repentance).
There is no limit to this - it is all possible, and indeed all necessary if we are to be clear about the nature of sin and of our personal failure.
But this is not paradoxical, complex, weird nor even difficult: the rule is that we simply repent every sin - everyone can do this, can do it now; and nobody is excluded by any personal deficiency.
It is a great gift - for by it any person can clear-the-decks, shrug-off paralysis and despair; enjoy the assured hope of salvation; and embark on the adventure of being a Chrstian as best they may.
(And with all kinds of divine helps and aids coming to awareness, that were unseen before - which may well lead to unexpected successes.)