Conscience is the inner sense of right and wrong. Conscious means awake or aware. A guilty conscience. Conscious of the noise. Diction as a set is in word choice.
Moral sense versus awake
If the sentence is about guilt or ethics, use conscience. If it is about being awake or noticing something, use conscious. Science with an extra n is the usual miss.
Discreet versus discrete is another look-alike, in discreet versus discrete. Affect versus effect is in affect versus effect. Grammar overall is in ACT grammar rules.
The bottom line
Right and wrong: conscience. Awake or aware: conscious.
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