有两个几乎是相反的意义：（正面的）渴望，急于；（负面的）担心，生怕。如何辨别，取决于：1) 单词搭配；2) 搭配词的词义；3) 上下文。
(1) 如果anxious单独用作定语或表语，意义就是负面的。
an anxious day焦急的一天
an anxious question令人焦虑的问题
the anxious class（美国）不安的阶级，因为收入提高不了而为日后养老发愁的中产阶级。
It's time to be going home, your mother will be anxious. 该回家了，你母亲会焦急的。
(2) 如果搭配是to be anxious to inf.，to be anxious for somebody to inf. 或to be anxious about + -ing，就是正面的“渴望”、“急于”。这个意义，尽管有一些语言学家反对，但实际语言中常常使用。
She's anxious to get abroad. 她渴望到国外去。
My parents are anxious to meet you. 我父母盼着要见你呢。
Anxious to please, he offered to cook dinner. 他急于讨个欢心，就自告奋勇说由他来做饭。
We are anxious for him to return home safely. 我们热切盼望他平安回家。
The movie is so anxious about covering as much of the novel as possible that it never gives the actors any breathing space. (Newsweek, May 29, 2006, p. 53) 影片急于尽可能多涵盖小说的情节，弄得演员们一点喘口气的空隙都没有。
Even without his books, Don Quixote set forth once again, anxious as before not to lose any time, “for he could not but blame himself for what the world was losing by his delay...”(Malcolm Muggeridge, Punch, April 8, 1953) 尽管没有了他的那些书，唐吉诃德仍然再一次出发上路，像从前一样急于分秒必争，“因为他如果耽搁了，全世界就要遭受损失，这个过错他是担当不起的...”
但anxious about后面不是-ing动名词而是名词时，意义是负面的“担心”。
... will ease the professor's mind on a point that he seemed anxious about.(George Bernard Shaw, Cashel Byron's Profession) ...可以让教授对一件他似乎担心的事情放心。
... people are afraid of losing their jobs and their homes and are anxious about a possible recession. (US News & World Report, Jan. 14, 2008, p. 16) ...人们害怕失去工作，失去住房，担心可能经济衰退。
anxious lest则当然是负面意义的“担心”。
He was anxious lest they were broken and thus make an evil omen. (Pearl Buck, The Good Earth) 他担心东西破了，兆头不好。
(4)如果搭配是to be anxious for something，意义可能正面也可能负面。如果这个something是定指的正面利害关系，则与to be anxious about something相同，anxious意义为负面的“担心”。
I was anxious for their safety when I heard the news. 我听到这消息，就替他们的安全担心。
Distraction display very rarely occurs except when a bird is anxious for its nest and eggs or young. (Edward A. Armstrong, Bird Display and Behaviour) 一只鸟除非担心自己的鸟巢和蛋或是小鸟，否则很少出现分神的现象。但如果something是不定指的事物（亦即尚未拥有的事物），则anxious意义为正面的“渴望”。
The boy is anxious for a bike. 那个男孩渴望有一辆自行车。
civil servants anxious for promotion盼望升职的公务员。
His sisters were very anxious for his having an estate of his own...(Jane Austen, Pride and Prejudice, Chapter Four) 他的姐妹们倒反替他着急，希望早些购置产业......
her sister... for whose happiness she grew daily more anxious... (Jane Austen, Pride and Prejudice, Chapter Twenty-Three) ...她关心姐姐的幸福一天比一天来得迫切...
(5) 如果后面有以that引入的从句，意义可能正面也可能负面。如果从句中谓语动词组的功能词（operator）是may (might), will (would)之类表示可能性的助动词（属陈述语气），或是直接用动词的陈述时态，意义就是负面的。
They were anxious that the enemy might turn south and attack the city. 他们担心敌人会掉头向南进攻这座城市。
Retailers are anxious that consumers may cut back on spending. 零售商担心消费者可能削减支出。
I am getting more and more anxious that gene doping may be misused by athletes and coaches. 我越来越担心基因兴奋剂会被运动员和教练们所滥用。
We are anxious that technology will be turned against us by terrorists. 我们担心科技反而会被恐怖分子用来对付我们。
We're anxious that doing the opposite would be something wrong. 我们担心反过来干会不会错了。
You don't need to feel worried and anxious that pregnancy is playing havoc with your hormones. 你不必忧虑担心怀孕会破坏你的激素。