It is just the mind-set of a person that makes the language hard.
All wehavetobethankfulofalltheblessingwevereceived.
Im afraid to bite off more than I could chew.
mind-set不应该是复合形容词吗？怎么样区别复合形容词和复合名词？
不应该是bethankfulfor吗？
todomorethan是什么结构，没办法理解。
1 mind-set为名词，意为思想倾向、心态。并不是连字符连接的都是复合形容词。有疑问你应该查词典。另外看该词是作主语、宾语还是定语。前者为名词，后者为形容词。
2 be thankful 一般后接介词for表示对什么心怀感激。但也偶有用介词of的。COCA语料库就有用of的例句。比如：
We also arethankfulofall nurses and nursing students who participated in this study.
Imthankfulofthat.
Youd think the rich would bethankfulofwhat life has given them.
所以，你阅读时了解有这种使用方法即可，自己写作时用for.
3 Im afraid to bite off more than I could chew.
more为代词作bite off的宾语，than引导比较分句修饰more。字面意思是一口咬掉的量超越自己能咀嚼的量。引申的意思是做自己力所不及的事情。
