I was installing a light in an office today.  I hate these kind, very difficult to install.  I was on an eight foot ladder and there were people all around working.   I put the fixture in the space and pulled back this spring loaded clamp, and bam, it closed right on my thumb. 
   It hurt.   
   A lot.

I just stayed calmn,  breathed and said that it didn't hurt.   I had a hard time pulling back the clamp with only one hand.   I was clamped for about two minutes.  The whole time I breathed and lowered my heartrate.    I finally pried it open with my screwdriver and it snapped into place.
    I didn't want to scream in a crowded office.  While I was waiting for the frieght elevator, I realised that through concentration I bypassed some physical damage.   

I have willpower defence!