system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How come my body can heat up so much when I'm anxious but it fells like it barely does anything when I'm cold.
gpt
When you enter a cold environment your body starts preparing for  extended exposure and begins conserving body heat through various means such as blood vessel constriction in the extremities.

Being anxious (and not out in the cold), is a stress reaction that does almost the opposite - gets the body and muscles ready for a fight-or-flight scenario, which among other things *increases* blood flow.

Thus one results in you feeling cold (even though your body is *preserving* heat), and the other gets your muscles prepped *at the expense* of producing and losing extra heat.