宾语从句的主语可以省略吗?I pledged (that I) would never be late again.括号

从句里面用的是陈述句语序,主谓宾.
that 可以省,但I 应该不能省.
从句独立出来说也是一个句子,主语掉了这个句子就不完整了.
除非在“I don't know what I should do,”就可以变为“I don't know what to do”.
不能只把I 省掉,首先要句子完整了,再谈得上优美.