CL 528, 529 - Committing vs. Refraining from Evil

CL 528

. . . anyone who purposefully or deliberately
acts against one commandment acts against the rest,
since to act purposefully or deliberately
is to deny altogether that the action is a sin,
and anyone who denies the existence of sin
regards it as nothing
if he acts against the rest of the commandments.

CL 529

Something similar is true in the case of people
who are in a state of good from the Lord.
If they from their will and intellect or
purposefully and deliberately 
refrain from one evil
because it is a sin,
they refrain from them all;
and this still more if they refrain from several.
For as soon as anyone purposefully or deliberately
refrains from some evil because it is a sin,
he is kept by the Lord
in a purpose to refrain from the rest.
Consequently, if he then does evil unwittingly
or under the sway
of some overwhelming lust of the body,
still it is not imputed to him,
because he did not purpose it to himself,
nor does he defend it in himself.
A person comes into this purpose
if he examines himself once or twice a year
and repents of the evil that he finds himself.
Not so one who never examines himself.