If you do something pertinaciously, you keep doing it, or keep believing it, and you will not let go. This is stronger than “trying hard.” You stay with it when it is difficult, when other people are tired of it, and sometimes even when the facts have moved on. Dictionaries can make the word sound like clean courage, though actually it often leans a little toward stubborn: the person holding on may feel brave, while everyone around them feels the grip is too tight. You will almost never hear this in a shop or in the school corridor. It belongs to books, essays, and rather formal speech. In everyday talk people say stubbornly, wouldn’t give up, or kept on.

執拗地；頑固地（書面語，帶「抓太緊、不肯放」的味道，不只是「很努力」）