The phrase "keep nose to the grindstone" refers to hard work and diligence. There are a variety of synonyms that can be used to convey a similar meaning. "Stick to it," "persevere," and "stay focused," all convey the idea of maintaining one's efforts and staying on task. "Press on," "keep at it," and "stay the course" all indicate the importance of perseverance and determination. "Stay committed," "remain steadfast," and "maintain one's focus" all suggest the idea of staying dedicated to a task or goal despite obstacles or distractions. "Stay on track," "stay the course," and "keep at it" all suggest the importance of maintaining momentum and staying focused on one's goals.