In the Old Testament we read of many sacrifices offered to God on altars - in which an animal was slain. But we read in Romans that we are to be "living sacrifices". But what is the difference between being a living sacrifice and a dead one? For us, it is the ability to leave the altar. We are not laid on an the altar unable to do anything about it - we choose to be on the altar (and we can choose not to be).
We read of those who have died for Jesus, but how many of us live for Him? To do so, to die daily to self and live for and in Christ, is not a calling of great service - it is merely our reasonable service. There is much pretending that as Christians our life is still ours to do as we choose, but the reality is that if we live as we should - we don't live, we die and we allow Christ to live through us.
I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service.