Sukkot Sukkah Sukkos

What is the celebration of סוכות ממש?

What was the נס? It seems very basic that we went into huts when we left מצרים out in the desert and needed shade?

A סוכה is a דירת עראי.

 The בני ישראל in the  מדבר followed ה' when they were לכתך אחרי במדבר בארץ לא זרוע

The celebration is, as opposed to other ימים טובים, where we celebrate  ה' doing a miracle for us such as פסח, a celebration of us leaving a civilized place and following ה' into the desert. We are celebrating בני ישראל's ultimate אמונה.

When man is fully reliant on God that is the ultimate reason for celebration. סוכות is the only חג called חג לה' as it says וחגותם חג לה' שבעת ימים

This is really the source of ultimate שמחה.

The גמרא says a story in ע"ז where he does not have ultimate שמחה.......................

The only way to have complete peace of mind is to feel fully secure in a given situation. The only way to truly feel fully secure in one's situation is to know that nothing can come in the way of his comfort. That can only come with knowing that God is in his corner protecting him. The סוכה represents the עראי of עולם הזה on one hand but also the security of being enveloped by the שכינה on the other hand. If one can be מוסר נפש and go out of his "protective" environment of עולם הזה such as the בני ישראל did in the desert, he can then appreciate everything that God has given him with full security that no power in The world can take it away from him and that feeling, and that feeling only. brings full and complete שמחה. That שמחה will stay with him in this world and the next and therefore even the knowledge that this world will come to an end at some point for him it wont take away any of the security and שמחה that he is feeling as it will be a seamless transition to an even better world, the world of real שכר. 

The סוכה  represents real joy in עולם הזה and the way to enjoy עולם הזה too.