Full Idea
If you have reasons for your belief, they should be considerations you could in principle cite, or give, to someone who doubted or challenged the belief. You can't give some else a non-propositional state like a headache.
Gist of Idea
Reasons for beliefs can be cited to others, unlike a raw headache experience
Source
James Pryor (There is immediate Justification [2005], §6)
Book Reference
'Contemporary Debates in Epistemology', ed/tr. Steup,M/Sosa,E [Blackwell 2005], p.193
A Reaction
On the whole I agree, but if someone asked you to justify your claim that there is a beautiful sunset over the harbour, you could just say 'Look!'. Headaches are too private. The person must still see that the sunset is red, and not the window.