
Originally Posted by
RedFox
Normally, a russian sentence has structure topic + comment:
Я уезжаю в Москву завтра. - "я" is a topic (i.e. what is your sentence about) and "уезжаю в Москву завтра" is a comment (i.e. information your sentence provides).
You cannot omit a pronoun if it is in the comment:
Завтра в Москву уезжаю я. (а не кто-то другой) - in this sentence, "я" is the main information, so it cannot be dropped.