"Oneself" is pretty formal and a little archaic too. I don't think I've ever heard anyone actually say it in a normal conversation. For example, you could say, "One has to learn to control oneself." I think the meaning is quite clear for you. Alternatively, "A boy (he) must learn to control himself." "A girl (she) must learn to control herself." "People (they) must learn to control themselves." I hope this solves your question.

I suggest using one-self when the related sentence can refer to anyone. I would only use himself when the related sentence is directly about a male. In general, you could use both in either situation, but to avoid offending anyone I suggest using Ine-self.

I don’t often see anyone use oneself. In a form, try to avoid using pronouns i.e. him. In this case, I would use ‘themselves’.

I occasionally use "oneself", but it is more common to use "yourself" instead. Using "one" and "oneself" in place of "you" and "yourself" makes it clear to the person you are addressing that you mean a person generally and not them. One can sometimes cause confusion by using "you" instead of "one" but it is mostly clear from context. The choice of using one or you is a decision one must make oneself.