In many parts of the English speaking world (UK,Ireland,Australia,Canada,and South Africa) “practice” is the noun,“practise” the verb.However,in the U.S.A the spelling “practice” is more often used for both the noun and the verb.Contrary to popular belief a significant minority of the American population also observe the distinction.If you are not sure about what a verb or noun is,it might be safer to just use the spelling "practice",as many Americans do!
在大部分英语国家,甚至是美国（部分人）,也是分别使用practise 和 practice 的.所以这里应该是practice makes perfect.使用名词形式.