I have also heard the phrase "Make the "truth(??)" your own". In fact, that is the title of one of the Kingdumb Maladies.
What does this mean? You can hear the "truth(??)", and know it by heart. But, what making it your own means actually believing it with your whole soul, without doubting. And, since the "truth(??)" is actually a pack of lies, this means not reading critical material. Because once you read apostate material and it makes sense, the "truth(??)" is more like a blatant lie and you will no longer believe it.
Their idea of having the truth in you (or making the truth your own) means following all the rules. Not just because of getting disfellowshipped. But, you have to actually believe that it is harmful to say "Happy Holidays" or "Merry Christmas" to someone. You have to be repulsed by Christmas decorations. The thought of doing fornication with someone you are attracted to has to make you puke, similar to doing fornication with your father or a dog. Plus, you are supposed to live for field circus, hoping for excellent results and getting disappointed when people are not home or if there are wasteful snafus while out there.
There is such thing as absolute truth. This is self explanatory. But, it is difficult to grasp the absolute truth when you have no scientific proof that anyone goes to hell or gets resurrected after death or that God exists (or, if He does, that He is actually not a Tyrant). There is such thing as truth according to the Bible, which may or may not be the absolute truth. Being in the truth in that sense means having a true understanding of what the Bible actually means, having come to that conclusion through independent research, and living to the best of one's ability according to the Bible. However, there is no such thing as truth according to the Watchtower Society for the simple reason that it keeps changing. What was true in that sense today is false tomorrow, and absolute truth (or even truth according to the Bible) never changes.