My mare /horse is laying down.
Meaning 'I was keen to go (out) but now I'm too tired'.
It is a tongue in cheek excuse alluring to the exhaustion of the means of transport: if my horse has laid down, I can't get anywhere.
Synonyms of se me echó la yegua are estoy raja estoy muerto me da paja me da lata
Used in US as well
"Tenía ganas de ir al bar, pero ahora se me echó la yegua"
