Self advocacy is usually discussed as a matter of confidence. It depends more on information: knowing what can be asked for, of whom, and in what form.
The skill has three separate components
Advocating for oneself requires identifying what one actually needs, knowing what the other party is able to provide, and framing the request so it can be acted on.
Confidence affects only the delivery. Someone highly confident who asks the wrong person for the wrong thing still gets nothing.
Treating it as a personality trait therefore misplaces the difficulty, and it leaves people believing the problem is who they are.
Knowing what is available requires access
Requests succeed when they match something the organization already does: an existing flexible arrangement, a training budget, a transfer process, an accommodation procedure.
That knowledge circulates informally, through colleagues who have made similar requests, which means access to it is unevenly distributed.
People outside those informal channels ask for things that do not exist, or fail to ask for things that would be granted routinely.
Framing determines how a request is processed
A request presented as a personal difficulty invites sympathy, which is not a mechanism for producing a decision.
The same request presented with a specific proposal and its effect on the work is something a decision maker can approve, decline or modify.
This is not manipulation. It supplies the information the other person needs to act, which vague requests withhold.
The response to a request is data
A refusal contains information about constraints, priorities and who actually decides, and asking what would need to be true for a yes converts it into something useful.
Repeated refusals of reasonable requests are information about the organization rather than the requester, and that reading is often resisted longer than it should be.
Keeping a record of what was asked, when, and what was answered also matters if the situation later becomes formal.
Practice happens in low-stakes situations
The skill develops through repetition, and requests where the outcome matters little are where the mechanics can be learned without cost.
People who have been socialized toward accommodation often have little practice, and the absence of practice is frequently mistaken for absence of capacity.
Where fear of asking is severe enough to affect health, work or relationships, that is a reasonable subject to raise with a therapist rather than to push through alone.