Why leave the shelter? (The Tale of the construction of my shell)

I don’t even remember when construction of the shelter started, but it happened somehow unnoticeably. When I was young it was nothing like a fortress, but just big opened space with easy access, welcoming everybody. I used to leave it quite often, it was a lot of fun outside and sometimes I would not come back to the shelter for days, but after a while I would inevitably return. With time passing by, the space necessary for my existence started to shrink. Fewer and fewer visitors would come by; it was probably because they became deeply involved in their own construction projects. A lot of things surrounding me ceased to be necessary any longer (pieces of furniture, interior details, etc.). Lastly the books that used to take up so much space in my life noticeably decreased in volume, as I realized I did not need so many of them anymore. Through this, the structure of my habitat was forming the next level of its space naturally, according to my developing needs. Certainly, it is obvious that one day my space will come to its single point and then the construction of the shell will be considered completed.