This way of thinking makes a lot of sense to me, but it sometimes is met with resistance in the context in which I find myself. "No one is worthy but Christ!" is the most common refrain. Behind such language is a Protestant concern with maintaining the central role of grace in salvation, which seems hard to square with Origen's talk about merit and worthiness. How are we to understand this?
Consider what Paul says in 2 Tim 2:
In a large house there are articles not only of gold and silver, but also of wood and clay; some are for special purposes and some for common use. Those who cleanse themselves from the latter will be instruments for special purposes, made holy, useful to the Master and prepared to do any good work (vv. 20-1).
Implicit in this analogy is a judgment of worthiness and value. A golden instrument is not for cleaning toilets nor a silver spoon for digging holes in the garden, not just because it happens not to be used for that purpose, but because it is intrinsically inappropriate for something of such value to be used in that way. It is beneath the value or worth of the instrument for it to be used for that kind of thing.
In the same way, I think, the work of the Lord is above some people. Paul warns Timothy earlier in the chapter to avoid godless chatter (v. 16), and he says that whoever cleanses himself of such things will be an instrument for special purposes. It is beneath the dignity of the work of God for someone who engages in godless chatter to try to preach the word, or to instruct others, etc. They are not worthy of such work, as their own habits and practices amply demonstrate, and so their work is apart from God's will and calling.
This is what I think Origen means by his language of worthiness. If a person is worthy of a work, then such work is properly undertaken by her. She is the right person for that work; she will not undermine it through vicious living or bad habits or sinful actions. It will not be wasted on her. So also Paul says: I thank Christ Jesus our Lord, who has given me strength, that he considered me trustworthy, appointing me to his service (1 Tim 1:12). He was worthy of being trusted with the work given him, in spite of his grave sinfulness, perhaps on the basis of some other virtues of his: fidelity, hard work, determination, and so on.
This talk about worthiness is important because we have to recognize the gravity of the things we are dealing with as Christians. To preach the word of God to other people, for example, is a huge responsibility: we are dealing with the reputation of God and Christ, as well as with the great story of salvation through the sacrifice of Jesus, repentance from sins, etc. W are not dealing with small things but with huge things, the hugest things, and for that reason, we ought not to seek work or ministry that is beyond us. We ought sooner to make ourselves worthy of it by being disciplined, faithful, serious, etc. To entrust something precious to someone who couldn't care less would be foolish and unjust of God.
I have to take this message to heart, because I preach often. If I am not worthy of the work I am doing, or if I have disqualified myself from my calling through various sins and bad habits, then I am only doing myself harm in trying to steal a ministry of which I am not worthy.