As I understand it, nikdy means never, but you still negate the verb, unlike in English. It is sort of "you never not listen" although of course in English we avoid the double negative and say "you never listen."
Actually to add to Vala's reply. Czech sentences often REQUIRE double negation. TY NIKDY PLÁČEŠ. would confused everybody if you never cry or ever cry or never not cry or what in the world is up with you and crying. Just does not make sense.