You can't slacken off because you know someone can take your place.
这让你必须努力训练，你不能松懈，因为有人打算抢走你的位置。
He accused the government of slackness and complacency.
他谴责政府的懈怠和自满。 I was lax in my duties.
我对本职工作马虎松懈。
slack muscles
松弛的肌肉 taut:http://www.etthink.com/thread-284315-1-1.html
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