Where are we moving again?

Katherine sent me this:

On October 3, the Board on Geographic Names (BGN)
unanimously voted to change the BGN standard
transliteration of the spelling of the Ukrainian capital
to 'Kyiv'. This decision affects the whole USG, although
'Kiev' remains the BGN conventional spelling for this
city.

So, as I understand it, if I am transliterating from cyrillic, I must write Kyiv. If I'm just writing it, I write Kiev. What if I am just writing it, but in my head I am thinking about cyrillic? So confusing.