"I do not want to join the party" would not make as strong an impression on your listener as "I do not want to join your party, PERIOD!" It means something like: I do not want to join the party, and that is my final word! So stop asking me! If you were writing this, the little dot in "I do not want to join the party." is very difficult to see. But if you write the actual word, the reader will get the meaning that you are very serious and are not going to change your mind.

It means "end of discussion" (shortened in conversation to "end of") or "ever". The sentence may also have been "I don't want to join the party, end of." or "I don't want to join the party, ever."

Thank you very much, I understand the difference.

Gulmira: A few minutes ago, I just read this sentence: "[The name of a country in Europe] is part of the euro-zone, full stop." While we Americans might use "period," it appears that other English speakers might prefer "full stop." James