先分析这句.I felt so annoyed and upset that I put on a coat quickly and went downstairs,ready to abuse the one who had spoiled my beautiful dreams..
其中so ...that...是如此...以至于...的意思,引导一个结果状语从句,这里的T单位是I felt so annoyed and upset ,后面接了一个从句that I put on a coat quickly and went downstairs,而ready to abuse the one who had spoiled my beautiful dreams..是另一个表伴随的子句.
再分析这句：However,when I got closer and found out what happened,my attitude totally changed.
这句话与你给出的句型很相似,when I got closer and found out what happened,是一个表状态的从句,主句是my attitude totally changed.也是一个T单位,2个字句.
在'He stopped and he sat down on the soft grass'
这句话中,'He stopped和 he sat down on the soft grass' 中间的连接词是and,两个动作是并列的,没有谁轻谁重谁主谁次之分,所以有两个T,表示两个句子都是完整的.
我再跟你解释一下,所谓T,是一个完整的句子,一个完整的句子,必须要有一个谓语,如do,stand,speak.但我们常常将非谓语作为谓语,如he went in,shaking his hands.这句话中只有went 是谓语,shaking在这里只是非谓语,表示伴随动作,是次要的,所以这句话有一个T,两个子句.再如he went in and he shook hands with us.这样就是两个T,因为这句话中went 和shook没有主次之分,两个动作表示并列,是两个完整的句子,即有两个T.