Another subjective element to recoil is what I call the "Ohhh this is going to HURT!" frame of mind.
If you hand someone a rifle and tell them how to hold it, but then say "Hold on tight, that thing is going to kick like a mule", they will inevitably brace themselves, hesitate, flinch, and Then pull the trigger. (and tell you, just how right you were when you told them it was going to hurt)
Take that same gun and hand it to a similar person, tell them how to hold it right, and tell them its a "small, light caliber that a kid could handle" and they will probably fire it a few times and hand it back with no real sign of discomfort.
And while I'm at it. How about adrenaline or even distraction? Ever notice that when the buck of a lifetime is standing in front of you, or when a grouse suddenly bursts up and surprises you, that your gun never recoils.
Basically, if you are excited or focused on something other than the recoil you probably won't notice it nearly as much as if you are carefully taking aim at a paper target and focusing on "holding the gun properly"
Perception can be a funny thing.