"Latin: Incurvatus in se" (Turned/curved inward on oneself) is a theological phrase describing a life lived "inward" for self rather than "outward" for God and others.
Paul the Apostle wrote of this condition in the Epistle to the Romans 7:15, 7:18-19:
For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. [...] For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. For the good that I would I do not: but the evil which I would not, that I do.
It was perhaps Augustine of Hippo who first coined the phrase incurvatus in se. Martin Luther expounded on this in his Lectures on Romans and described this state as:
Our nature, by the corruption of the first sin, [being] so deeply curved in on itself that it not only bends the best gifts of God towards itself and enjoys them (as is plain in the works-righteous and hypocrites), or rather even uses God himself in order to attain these gifts, but it also fails to realize that it so wickedly, curvedly, and viciously seeks all things, even God, for its own sake."
This was later extended by Karl Barth to include other sins beyond pride. It is also believed that, even though people are justified by Jesus dying on the Cross, they still possess a propensity to sin against God because of this condition (i.e. simul justus et peccator).