How do people do it? they do it the same way they do everything else. Hopefully you learn what you have to, if you did not, or do not remember what you learned, hopefully you have a Rav to guide you.
This is true of everything in life, not just going out to work.
Take an Avreich sitting and learning. When is it appropriate to interrupt ones learning and do a chessed and when not? Does it depend who the chessed is for? Does it depend if others are around? Does it it depend on the type of chessed?
Take the average housewife. She cooked a pot of soup. It is cooling on the table and sees bugs floating on top. Does she spoon out the bugs and eat the soup? Check for more bugs like she was doing bedikas chametz? Does she have to throw out the whole pot?
Take a bachur in the dormitory. He is trying to fall asleep but he is hot? Can he open the window to cool off? Does he have to consider his roomate who makpid not to have the slightest hint of cold in the room?
People learn. If they dont, hopefully they have someone reliable to consult with. This is true for all people in all walks of life. It is not limited to people who go out to work.
Learning all three “Bavas” will not prepare someone for the workforce. In addition to Choshen Mishpat, there are very relevant halachos of Even HaEzer, Orach Chaim and Yoreh Deah that apply as well. Its a good thing most people dont believe they learned everything they need to know while in Yeshiva. The expression “Live and Learn” is quite appropriate.