Wikipedia defines motivational internalism as the belief that:

there is an internal, necessary connection between one's conviction that X ought to be done and one's motivation to do X.

I want to view this as a morally necessary connection. One should do what one ought to do, and this serves as the definition of "ought".

You will note that I am using circular definitions. That is because I can't define "should" except in terms of things that have a hidden "should" in there. But I am trying to access the part of you that understands what I am saying.

The useful analogue is this:

modus ponens: "If you know 'A', and you know 'If A, then B", then you know B"

It's a circular definition getting at something which you can't put into words. I would be wrong to define "If-then" as something else, like maybe "If A, then B" means "75% of elephants with A written on them believe B" because it's already defined.

Does that make any sense?