The official English of Lavi's scene is...probably not very good, from what I can tell. Which is understandable, this whole scene is tough. The official and fan translations say completely opposite things at several points, and I'm not sure which of them get it right.
So instead of getting too caught up on the exact wording of each translation, we're gonna go with vibes and context and stuff.
There's a big focus on how the Bookmen aren't supposed to give their heart, aka become personally invested, to anything, and how pointing this out hurts Lavi. Dream!Junior says these plain old facts like they'll make Lavi feel sorry for himself, and they do.
This scene has been analyzed by plenty of people before, but what I take from this dialogue is: Lavi actually isn't happy being a Bookman, huh? He is miserable and pities himself this lifestyle he was raised in; just laying out the reality of how he's supposed to live is enough to hurt him. He recognizes how empty and lonely and condescending the whole Bookman philosophy is, but can only say "I know...!". He actively thinks this whole deal sucks ass and still accepts it, and can't imagine living any other way.
Does Lavi know the previous Junior bowed out? Or rather, gave his "heart" away? Does he even realize that's an option?
Meanwhile, Allen's fight also involves the matter of the heart, but for him, rather than his heart being his weakness, it's undoubtedly his strength!
Lavi and Allen make for good foils. Neither of them have a "real" name, or home, and both hide behind constructed personas to keep the world at a distance, but on the inside they're completely different. Allen's identity was stolen from him, while Lavi threw his away. Both of their masters have ties to the 14th and know far more about the past and the war than they share with their students.
This post has been sitting in my queue for about two months and previously read:
"Considering Bookman Juniors are named after the record they're recording, and that the previous and current Juniors are working on the same record of the Holy War, just from opposite sides, it's likely the previous Junior's name was also "Lavi" just like the previous Allen's name was "Allen". "
Which is now completely confirmed.
There's a matching set of each of our protagonists in both past and future. Just like there was a past "Lavi" and past "Allen", there was a past Kanda too. Essentially, every character in DGM has a "past" counterpart, whether an actual version of themselves or a narrative substitute, ie the previous generation of Noah and the current, or Anita and her mother. Of our four major characters so far, only the Lenalee analog for the past is still missing.
This is also one of the reasons I thought for so many years that the previous Bookman Jr and Past!Allen couldn't possibly be the same person, but until this year, if I pointed that out any DGM reader interested in theories would have laughed me right out the door...