General Brazilian
manter-se firme / permanecer resoluto
Most common and widely understood across Brazil
Rio de Janeiro
ficar firme / manter o pé firme
Colloquial expression emphasizing steadfastness
São Paulo
manter a determinação / seguir firme
Common in business and professional contexts
Portugal
manter-se firme / permanecer resoluto
Similar to Brazilian usage; 'manter posição' also used