Hi
Human beens are predisposed to hate losing way more than they love winning - Its one of the strongest survival instincts in a dangerous world.. The evolutionary advantage you're referring to is a by product of parts of our brains that haven't really evolved much since we were living in caves.
Imagine back then when we didn't have all the security & comforts we have today - every day you literally had to survive. The loss of that antelope you were chasing that got away can literally impact your survival. The closer you get to the survival boundary, the more chances you will take to secure vital resources. In that envionment risking more is evolutionary advantage because you had no other options and if you didnt risk, you'd probably expire. The more you risk, the more you increase the chance of you living another day.
Back in today's world those exact same brain regions are still operating - we've the same brains as we had 20,000 years ago. So that loss you're sitting on in that Apple trade is hitting exactly the same buttons. Your brain is thinking "I'm losing a resource, quick do something, risk more to get it back, or you'll perish", so you risk more, maybe chase the loss. But really you won't perish (depending on your wife's support for this trading thing!) and risking more will probably wipe you out eventually.