这句中的that可以省略吗

这句中的that可以省略吗
They say at the end of your life,you regret the stuff you didn't do more than the stuff that you did.
最后的that是不能省略的吗,为什么,是从定语从句的角度考虑还是别的语法?

They say(THAT) at the end of your life,you regret the stuff(THAT) you didn't do more than the stuff that(THAT ) you did.
第一个that是宾语从句的连接词,可以省略.
第二个和第三个that都做定语从句中的宾语部分,也可以省略.
再问： 宾语从句的连接词都可以省略，还是看它做句子中什么成分？
再答： 宾语从句的连接词that一般都可以省略。that引导的只能是陈述句。