Each job involved pulling a relatively delicate fiber optic cable through a network of underground street vaults, locating a buried conduit without a map by digging for clues, bringing the exposed cable from the sidewalk to the outside unit on the home, drilling an entry point in the home, securing the cable running into the home, teaching the customer how to control the system with their cellphone and then trenching and burying the entire line back to the street. I usually did this twice or three times a day.
I started loading semi-trucks. Basically a hardcore workout at an intense speed. Moving between 110 degree+ trailers constantly and using safety methods to stay alive. I learned from painful experience how to manage the risk of heat exhaustion and stretch to avoid injuries.
Later I moved to air load. That was more specialized and required learning how to strictly implement a very specific set of rules to quickly identity different hazard labels and properly arrange separation between the packages based on the type of hazard. It was all about attention to detail and knowing the standards by heart.
Everything at UPS was about balancing metrics and safety. You wanted to have good metrics, but you also didn't want to injure yourself by going past your limit. You had to find the right balance between the two.