Having been on a sports team and been in combat situations, their is definitely parity between the two. I never once looked at the situation I was in playing football and said "This is stressful, but it least it isn't life or death!" At that moment, it's all there is. The pressure is just as real. I never once looked at my LPO and said "You know, all that stuff I went through before wasn't tough at all compared to this." Sports prepared me accurately to handle the pressures of life and death moments. Sure, being in armed combat was more stressful, but it's not like I was competing at the Olympics in football, either.
The truth is, you don't know how something will pressure you and how that pressure will affect you until it does. There are people who find social stress harder than life or death decisions, hence you get people who die in fires because they want to save their possessions or get dressed before they leave the house. People who lose their earnings in the stock market or other financial collapse often choose suicide over the disgrace of that loss to their friends. My wife worked at a country club in 2007-2010 as a massage therapist, and the suicide rate there was unbelievable after the housing bubble burst. These people weren't broke, but lost a fair bit. It was very likely the disgrace of the loss that caused several of them to crack. You think you know what real pressure is? You probably do. But don't think that the pressure someone else is facing is less than yours simply because the stakes are lower to you. The importance of events is different to everyone, and that is what makes an event stressful or not.