system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why that, even if I just peed, getting in the shower makes me pee more, no matter how much or what I try to do to empty my bladder before I got in?

Also with getting in the pool or the bath, does the warm or cold water actually affect you physically? Or is it completely psychological?
gpt
Running water makes you pee due to hard coded evolution. 
If you hear running water it means you have a source of water to drink so the body is willing to dump the extra with wastes. 
Basically, it tries to ensure that you have adequate water available before getting rid of some.