I don't understand the JW newspeak very well, but "guarding one's conscience" IMHO is another word for "conditioning".
They are not the same, but one follows the other. First the conditioning and then guarding it. I was lucky because I refused to be conditioned.
As soon as I saw the proof that to be a JW is to "trust in their governing body" I left. I had many doubts before that time that they are "the truth", so it did take me awhile to leave them. One reason why I stayed for some years is that I wanted to know what would happen to them, but I found out much more about them since I left, which is, I think, ironic.
Guarding one's conscience.
Proverbs 23:19
Listen, my son, and be wise, And direct your heart in the way.
2 Kings 10:31
But Jehu was not careful to walk in the law of the LORD, the God of Israel, with all his heart; he did not depart from the sins of Jeroboam, which he made Israel sin.
Deuteronomy 4:9
"Only give heed to yourself and keep your soul diligently, so that you do not forget the things which your eyes have seen and they do not depart from your heart all the days of your life; but make them known to your sons and your grandsons.
Luke 6:45
The good man brings good things out of the good treasure of his heart, and the evil man brings evil things out of the evil treasure of his heart. For out of the overflow of the heart, the mouth speaks.
Mark 7:21
For from within the hearts of men come evil thoughts, sexual immorality, theft, murder, adultery,
Matthew 15:18
But the things that come out of the mouth come from the heart, and these things defile a man.
Matthew 12:34
You brood of vipers, how can you who are evil say anything good? For out of the overflow of the heart, the mouth speaks.
Proverbs 4:23
Watch over your heart with all diligence, For from it flow the springs of life.