Unfortunately there aren't too many existing compilations of grant, fellowship, and job application submissions, but there are some! Hopefully they can help provide a template for your own future application.
|NDSEG compilation of essays||A small list of essays for the NDSEG competition only from the 2019-2020 cycle so far; however, perhaps the largest public collection of such essays|
|NSF compilation of essays and reviews||Alex Lang build this popular spreadsheet that links to NSF GRFP essays and reviews from winners and non-winners alike|
|Open Grants||A list of submitted applications across grants, though there seems to be a tilt toward faculty members|
|Successful Job Applications and Grants||The job and grants applications in this repository don't touch upon cognitive neuroscience, but they are nonetheless open which in of themselves makes them useful guides, regardless of their topic; and of course, more resources could always be added|