Once done is done. We can never take back something that we have done. There are many choices in our lives that we will always regret and will never forget. Those choices that we have made changed us, molded us to a better person that we are right now.
The Tatami Galaxy is simply the resemblance of the author’s experiences back when he was still at school. I haven’t seen any written interviews about this work of him yet but I am pretty sure that he wanted to share something epic to his personal and worldwide readers the experience that he had as a school guy.
Also, the Fortune Teller gives an additive element to the story. It is like playing a game where you have to go through a save point and sooner save the game for safety purposes. The Fortune Teller always has a clip on each episode of the anime adaptation that gives colors and new device for the story itself.
The novel was finished 10 years ago and has won tons of manga illustration awards locally in Japan. A season 2 may not come because of the lack of materials for an adaptation. Who knows? Maybe a spin-off would be released or a similarly anime by the same author would make a blast again.