It's adj for sb to do sth和It's adj of sb to do sth有什麽区别？

前一个：做什么什么事对你如何如何
例：it's
good
for
you
to
learn
English,学英语对你有好处
后一个：做什么什么事说明你本来就如何如何
例：it's
very
nice
of
you
to
help
me
,你真是太好了，能来帮我