[...Definitely not going to voice the thought of "Maybe it'd be nice to forget" then. Even if Gold's kind of dreading having to miss so many people he might never meet again when he goes home. But if this is something Trip's scared of, Gold will reassure him.]

I don't make friends easily. You're one of my first friends ever, so making other friends won't make me forget about you.

[Stated with absolute certainty, because it's true. (And vague enough that even if his memories end up getting erased by drifting back home, the statement is still true!)]