过去时的句子后面加了一个doing sth的词组,为什么?

题目

过去时的句子后面加了一个doing sth的词组,为什么?
我知道有一种是作为时间状语.但是这个句子呢——Jack went back to his work,feeling pleased with himself.这句话中的feeling pleased with himself感觉不像时间状语,那应该是什么?还有没有其他的用法?再附加一个句子：She said to me,smiling.
Jack went back to his work,feeling pleased with himself.这句话之前的故事情节是有人向Jack寻求帮助，但是他拒绝帮助别人。

答案