In God's good providence, each servant is essential and yet replaceable in the mission. This comes as a relief to people with a tendency to over-serve.
You've heard the aphorism that “20% of the people do 80% of the work” at church. And you probably wince because you know it‘s even more disproportionate in many congregations. Having been among the "few who do", I deeply appreciate my brothers and sisters who serve eagerly on behalf of the Body. But I also worry about them burning out. There is real danger in service that flows from misunderstandings about our calling (and creaturely limitations) in Christ.
Recently, I've been meditating on how, in God's good providence, each servant is essential and yet replaceable in the mission. Because the Father ordained good works for each Christian from eternity, we have specific tasks no one else can fulfill.  But when our predestined service is complete, in one area of ministry or in our lifetime, the Lord raises up someone else. Raising new laborers might involve a lot of effort from our perspective, but it is effortless for the Holy Spirit. What this means is that while God uses our gifts and effort to further the Kingdom, His mission never depends on any one in such a way that the Church stands on humans.
This comes as a relief to people with a tendency to over-serve. Is that you? Do you ever feel guilty or anxious for not doing everything, knowing everything, and being everywhere for everyone? Recognize these qualities for what they are: omnipotence, omnipresence, and omniscience. Such attributes belong to God alone. Therefore, it is not Christ, but Satan, who lays a false burden on you to be super-human. “You can become like God” (Gen 3:5). 
Our Shepherd's yoke is comparatively easy. Jesus doesn't call you to complete the harvest single-handedly, but to pray for additional laborers to share the load (Luke 10:2). You can trust him to do so. After all, he is the Lord of the Harvest. Only when we accept creaturely limitations do we lean on divine power. Then we discover there is more rest in the Christian's heaviest labor than in the unbeliever's lightest relaxation.
1. Eph 2:10, ἔργοις ἀγαθοῖς οἷς προητοίμασεν ὁ θεὸς. Literally, “good works which God prepared beforehand." God's eternal preparation consists in decreeing certain ends, as well as the secondary causes and means by which they come to pass.
2. On this subject, I am indebted to Zach Eswine's book, Sensing Jesus (republished as Imperfect Pastors). He deals with the practical implications of this theme over the course of three chapters.