1Tim 1:19 having faith and a good conscience, which some having rejected, concerning the faith have suffered shipwreck
Why do shipwrecks occur? Because of shallow faith. Like the seed sown among stones these allegedly believe as first, and with joy, but when tribulation or persecution arises because of the word, immediately they stumble. Matt 13:5,21 Thus traveling on shallow waters they end up shipwrecked.
Others get shipwrecked by not taking heed to their conscience which corrupts it causing it to lose its effectiveness in directing the person, so these end up dashed against the rocks along the shore, not keeping to the course. Or one may have such an effect on the conscience of others. For it is written that "when you thus sin against the brethren, and wound their weak conscience, you sin against Christ." 1Cor 8:12 which causes them to stumble.
Therefore take take heed to your faith and your conscience.