try not to be too stressed.老大我看不懂这儿的 to be形式,

这是一个祈使句形式的句子,其省略的主语是 You.这个句子可以有两种解释：
指令、命令 —— You try not to be too stressed.
建议、指导 —— You should try not to be too stressed.
not to be too stressed：动词不定式作谓语动词 try 宾语.not to be 是 to be not 的非谓语形式,即人们在用动词不定式作非谓语时,习惯上会把不定式的否定词 not 提到不定式符号 to 之前.类似的句子还有：
I tried not to do that.
He asked me not to believe the rumor.
We have been advised not to learn bad English.
.

须注意的是,not to be/do 并非是唯一正确的用法,to not be/do 也有人用：
I tried to not be one of them.
I was instructed to not go there.
We asked them to not hold their aggressive attitude to us.
.