Animals that go into themselves!! we're all animals at the end of the day!

I started to look at a broader scale of introverted behaviours ...snails are a common animal/insect or whatever they are scientifically called? slimy little things anyway!
Snails retract and go inside their shells when they want to sleep , get some warmth and more importantly protect themselves against possible threat!!
The shell on there backs are a safe haven , a place they can curl up into and hide from the world!
Humans also have defence and protection mechanisms.... the term 'going into their shell' or 'gone into themselves' is a common methaphor for somebody who may be threatened or under some sort of stress!!
we can do this metaphorically or with clothing or both?
This observation again links me to my project so far as I am now on the track to looking at changes in behaviour due to everyday issues...positive or negative.