Don't slack off in your studies.

学习上不可懈怠。

Carpenter! Slack off the brake.

木匠，松开刹车。

We can afford to slack off a bit.

我们可以稍微偷懒一下。

Don't slack off.

不要懈怠工作。

Don't slack off, and focus on the task at hand.

别偷懒，并专注做手头的任务。