whistle in the dark
US /ˈhwɪs.əl ɪn ðə dɑːrk/
UK /ˈhwɪs.əl ɪn ðə dɑːrk/

1.
assobiar no escuro, fingir coragem
to try to make yourself feel more confident or less afraid by pretending to be brave or cheerful
:
•
He was just whistling in the dark, trying to convince himself that everything would be fine.
Ele estava apenas assobiando no escuro, tentando se convencer de que tudo ficaria bem.
•
Despite his brave words, I could tell he was just whistling in the dark about the company's future.
Apesar de suas palavras corajosas, eu podia dizer que ele estava apenas assobiando no escuro sobre o futuro da empresa.