I have no reference for what follows except the foundation given by the dictionary definitions; all the rest is deduction on the basis of inferences of my own and my understanding of English, which, let's hope, will not be found too much at fault. The problem lies in the basic ideas from logic: not anyone will identify the concepts clearly but someone familiar with the basic elements of this theory will perhaps benefit from the connections that are established.
(OALD) someone a person who is not known or mentioned by name
(OALD) one (formal or old-fashioned) used to mean 'people in general' or 'I', when the speaker is referring to himself or herself
Note: it is much more usual to use 'you' for 'people in general'.
(SOED) someone some unspecified or unnamed person; = SOMEBODY
(SOED) one 12 any person of undefined identity, as representing people in general; I, him, her, as an example, a person, anyone.
I believe personally that the difference between "someone" and "one" is to some extent the difference there is between the quantifiers in the mathematical theory of logic. There is bound to be a certain margin of inexactitude (possibly important), but "someone" seems to be often quantifying the enunciation existentially, whereas "one" will quantify it universally. This is embodied to a point in the definitions: we do have "a person" for both, but in the case of "one" this is qualified by "anyone" (all) and "representing people in general" (all), which it wouldn't come to mind to do in the case of "someone".
Someone is at the door. (Said otherwise: "There is someone at the door."; this is more or less the logical form "there exists someone at the door" (Proper diction must be forgotten in this task of coding meanings strictly.)
One is at the door.
Tell someone in the audience to explain the problem. (There exists someone in the audience that you can pick and tell to explain the problem)
Tell one in the audience to explain the problem.
In the present case the existential characteristic is less salient, rather hard to find in the terms but there is not possibility of a universal quantification, which the impossibility of using "one" tends to confirm.
When one is sick one/they goes/go to a doctor. "One" should be be taken as the same person in both cases.
When someone is sick someone goes to a doctor. "Someone" is not taken as the same person in both cases.
When someone is sick This will do in a restricted context, for instance, that of a team working in an environment at risk. In the most general context, beside using a formal sentence with "one", people use formulations such as "When you are sick you go to a doctor." or "When people are sick they go to a doctor." they go to a doctor.
In terms of strict logical quantification this comes down to this: For all people, it is a fact that if one is sick he/she goes to a doctor.
This is an ordinary anxiety that comes and goes and does not interfere with someone’s life.
The use of "someone" in this sentence portends a hard to define lack of generality, when we are in right to expect the greatest generality. Much better will be the pronoun "your" for instance.
- This is an ordinary anxiety that comes and goes and does not interfere with one's/your life.
In conclusion, we see that from the logical characteristics that can be inferred and from the examples, in the light of existing usage, we tend to find justified the use of "someone" when some individual is concerned and the use of "one" when all are concerned.