良心

The matter weighed upon his conscience.

She felt relieved of the burden on her conscience. / She felt that her conscience had been eased/appeased.

Act as your conscience leads/guides/bids you. / Follow your conscience.

to be fair; in all fairness/conscience

act as one's conscience dictates; act according to conscience

be stung by conscience; be conscience-stricken

have a guilty/bad conscience; have an uneasy conscience; feel the pricks of conscience; one's conscience is troubled

return to one's good conscience; the conscience is moved

have a conscience; be good-hearted

act against one's (good) conscience

go against one's conscience

have got no conscience; be conscienceless/heartless/ungrateful