百折不挠

be indomitable; be undaunted; never yield in spite of reverses; be undaunted by repeated setbacks; keep on fighting inspite of all setbacks

勇气

courage; bravery; nerve; heart; an effort of will; guts; character; spirit; bottle; pluck; spunk; grit; resource; balls; gumption; mettle; fortitude; have courage; have guts; have the nerve