A sentence can consist of an indefinite number of words, a run-on sentence isn't based on how many words are in it.
What makes the sentence a run-on is number of clauses, individual thoughts that make up the sentence.
"I am tired" is a clause. "I am tired I don't want to go to work make it STAP!!!" contains two independent clauses and a dependent clause not properly put together, and thus is a run-on sentence.
To avoid run-on sentences, try to consider punctuation: use "." and "," to separate complete thoughts into their own sentences.
"I am tired. I don't want to go to work, make it stop!"
