Something special for this day. As +Björn Fromén hinted to me, there are multiple ways to theorise upon a single example of Elvish poetry; +Roman Rausch does agree in this topic. It is just as plausible that actual linnyd employed not (or not merely) accentual patterns but quantitative ones: with a scheme of long and short syllables, not stressed vs. unstressed. This time, I attempted a trickier verse (at least for me, but possibly hinting that it's really complicated to compose any quantitative poetry in Sindarin whatsoever). Thus, if this is not a linnod, I honestly don't know what it is (I even tried to reproduce the contraposition of the original one).

Gwistiel aenad o chuil, ú-besso únad o chin.

[Whatever from life having changed, affect [you] nothing about yourself.]

gwista- 'change (trans.)' (cf. Q. (w)vista-)
aenad 'if anything, whatever' (cf. Q. aiquen 'whoever')
únad 'nothing' (ú + nad 'thing, it')
I suggest that a pronoun in a prepositional construction is mutated as the preposition orders; I don't think a grammatical lenition should be performed for the case is never accusative. Hence o chin instead of ** o gin.