怎样区分it is +形容词+to和it is +形容词+for?

前者to后接动词，后者for后接名词或代词

It is+形容词+of sb to do sth 是形容人的品质的，例如，It's kind of you to help me.It's nice of you to help me.

而It is+形容词+for sb to do sth则是形容事物的性质的，例如，It impossible for me to finish the job.It's hard for him to give up smoking.