أخي الـis تعود على none و none ((لا احد)) هي no one
عموماً لا عليك ، هذا تصحيح جملتك

The sacret of joy in work is contained in one word - excllence. To know how to do something well is to enjoy


the secret of joy in work is contained in one word, excellence. to know how to do something well is to enjoy

وهذه جملة جديدة

no one is infalible, every body probable do sometheng rong