小心to take note; to be careful

• 留心孩子们的教育

  take note of one's children's education

• 留心国际局势

  keep an eye on the international situation

• 留心听人家辩论

  listen carefully to their debate

• 可惜你对这一点没有留心。

  It's a pity that you haven't paid this any attention at all.