I was supposed to go for walks, a little further each day, without overexerting myself.

我该出去散散步，每天都稍微朝远走一些路程，没有累着自己。

As he played nearby, I was overexerting myself and practically cursing all the trees for having made such a mess.

他在一旁玩耍，而我一边辛苦地捡着树叶，一边咒骂这些树把我们的院子搞得这么糟。

If you are required to take a lot of courses, you should ensure that you have few other responsibilities so that you can focus all of your attention on your schoolwork without overexerting yourself.

如果你必须选择很大的课程量，你就必须保证没有其它职责让你分心，可以全身心地投入学习，不会疲劳过度。