Please use five idioms such as "casual, absent-minded, unknown, once and for all, cheerful" to expand into a paragraph.

He wrote many articles in obscurity, and every time he contributed enthusiastically, he always got no response. Now he stood by the mailbox, checked it casually, threw it in and watched the thick envelope disappear. He turned around and looked absent-minded. What was the result this time? Will anyone agree? He has no idea of once and for all, but hopes that more people can read his articles and realize his dream of becoming a writer! I hope I can succeed this time.