system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What is the numbing sensation that washes over ones body when confronted with a negative and emotional situation?

I'd noticed this feeling today because I've felt it for the fourth time in my life. I can recall it because it's very distinct. I primarily source it to depression but, for an example, I saw my ex of two years with another man today and immediately my heart seemed to slow down and thump harder and my entire body had what felt like a wave that still has my fingers tingling and as if I feel extremely numb

The other, more recent time I can recall this is when a very close friend passed away. 

What is this feeling called and why does it happen? Is this shock?

Sorry if my explanation is lacking. I'm unsure of how else to describe it.
gpt
it's the fight or flight response. Blood vessels contracting as your body redirects blood flow to vital organs, an increase of adrenaline, that changes the emotional and physiological makeup of our bodies. Feeling threatened or under stress brings it out.