9. It is useful to kick the shuttlecock every day.
每天踢毽子对你有好处。
还能这样说：
Daily kicking the shuttlecock does you good.
Kicking the shuttlecock every day will benefit you.
应用解析：
make oneself useful 做些有用的事来帮忙;
例如：My nephews tried to make themselves useful about the house.
我的侄子都想帮我收拾房子。
10. Kicking the shuttlecock has sharpened my appetite.
踢毽子增进了我的食欲。
还能这样说：
Kicking the shuttlecock whets my appetite.
I eat more since I keep on kicking the shuttlecock.
谚语：
Appetite comes with eating.
胃口越吃越大(贪得无厌)。
11. There is nothing as sanative as kicking the shuttlecock.
踢毽子是最有效力的医疗方法。
还能这样说：
Kicking the shuttlecock is the most useful way to keep healthy.
Kicking the shuttlecock is the most effective medical treatment.
应用解析：
sanative 有疗效的，有益健康的，治病救人的
12. I am not skilled in kicking shuttlecocks.
我不擅长踢毽子。
还能这样说：
I can't kick shuttlecocks well.
I am not good at kicking shuttlecocks.
应用解析：
show skill at doing sth. 显示做某事的能力;
be skilled in doing sth. 熟练做某事