I think in a way the human body is an organism that constantly 'takes in' things and has a need to out stuff too. Like exhaling for instance.
Vague? Yeah.
Well, 'things in' are what we experience via our senses (most likely more than 5). The things we see, read or watch, things we listen too, smell and taste, feel, etc. but also the air we breathe in, the liquids we drink and the food we eat. Other things we swallow.
There are things we take in as well but defining them one may get lost in 'new age' emo stuff but e.g. feeling empathy or sympathy is a human trait too. Not the best of traits I have but to give you an example of feelings of others 'taking in' by someone. Certain train of thoughts (neg/pos) we can think of are something we take in as well. We could've decided to stop thinking about them earlier, but didn't.
Hope that part is 'followable'. Mmmm. Add: personally I think it's sensible to look at what we take in everyday. ALL the things we take in. I tend to be too much in 'my head' and tend to forget a little what's good for the body and what's not. For my body, me.
Out? Stuff that needs a way out of one's system?
Carbon dioxide and other gasses exhaled, the content of one's bladder, the message left and flushed in the little room but also 'stuff not good for the body to keep in' in the form of perspiration, tears(?), or other forms of 'flegma'. The lack thereof, I mean.
There are also things experienced and thought about on a daily basis that need a way to get out too and the thoughts and feelings felt that don't, can turn into an obsession, I believe.
*Fuck beforehand I knew I was going to strand in the 'out' part.
Um, expression.. expressing things 'in', letting them out in one way or the other, is also very important, I think. Thinking that's where a lot of 'buggery' folks have is caused. Mmmm, maybe even more so for folks on the auti-spectrum.
Let it go, let it be, let it all out, express, maybe is, the new age-ish advice I should fully grasp here.
Dunno.