In Nehemiah chapter three, there is an extensive list of all the people who helped build the walls around Jerusalem - the city where the Hebrew temple dwelled (Challenge - go read Nehemiah 3 and count how many people it mentions as helpers in the building of the wall. Each person played their part and made way for the next person to play their part.
When it comes to manual labor, you can pretty much bet that I will be more than willing to play my small part and pass the work on to the next person. In other areas of life, however, it's not as easy for me. I can be a control freak. When I used to have group projects for classes, I would end up doing all the work for the projects. Were my partners lazy or incompetent? Absolutely not! I just struggled to put faith in them to get the work done. Honestly, the times that I just played my role and let go were the times the group did best on the project.
When it comes to being Salt and Light, I think there are two categories of Christians. There are the Christians who are control freaks and tend to try to make everybody follow Jesus and be Salt and Light in the exact way they do it and there are people who tend to let everyone else be Salt and Light in the world while they sit back and watch.
The beatitudes call us past both of those mentalities. Part of being Salt and Light is having the ability, wisdom, and foresight to step out of the way if it means providing an opportunity for someone else. Another part of being Salt and Light is having the ability to step up and step into any role that God may be calling you to.
The beautiful thing that Nehemiah chapter 3 teaches is that we are all a part of building God's Kingdom as Salt and Light in the world we live in. Some of us have a calling to step up and some of us are being called to step aside for others to have an opportunity.