There are a lot of people in the world whose life is primarily, and consistently, dedicated to their own self-justification; to explain to themselves and to others, that everything they are and have done, all their choices and experiences, were justified.
Secretly, they assume (more than 'believe' - they assume) that they never made a mistake, that everything which went wrong was somebody else's fault (or sheer bad luck).
Sometimes they are boastful, sometimes self-obsessed, sometimes (and this is especially common) they have mastered passive-aggressive rhetoric, so that their continual self-aggrandizement is disguised by a fake humility.
The passive aggressive self-justifiers regard and promote themselves as humanitarians, altruistic, charitable, activists on behalf of others, 'passionately' 'concerned' with 'justice'... or some such abstraction.
Often enough, self-justification is self-justified as a necessary response to the attempts of The System and of powerful people within it - to dictate our attitudes and behaviours.
That was the trap I personally fell into - continually justifying myself on the excuse that otherwise I would be subordinated to someone else's justification. A better known example would be Thoreau in Walden; which book is impaired by Thoreau's frequent self-justifications; his boastful but insecure assertions, his denigrations of others - to make more space for himself.
I call self-justification a secret art, because - although it is extremely common - it is secret from the practitioners, and seldom explicitly identified by those around them.
Perhaps because so secret and so seldom identified; it can have a terrible effect on a person; feeding upon itself. It is, indeed, a species of the sin of resentment (which I find a better description than the more usual 'pride'); a particularly insatiable and destructive sin.
Self-justification can and does lead to hell. I can easily imagine that even when all other sins were repented; someone would cling to their own self-justification - as a thing so precious to their self-regard that they would give-up Heaven itself in order to keep hold upon it.