Pitch your project
Part of demonstrating you've not succumbed to the previously mentioned Miranda Syndrome involves clearly situating your work within the existing scholarship. In some respects, the purpose of this task is similar to that of a literature review. Both require you to gloss the relevant scholarship, and carefully select those works you see your project engaging with most directly; in a journal article, the scope of this is simply (though significantly) reduced, and you can focus less on describing the arguments of other scholars and more on articulating how your work engages with or challenges theirs.
Further, you'll need to convince your reader why your contribution to the scholarship is important. It's not enough to simply document your mastery of a body of knowledge and present your new findings, however intrinsically impressive you believe those findings to be. You also need to explain the broader ramifications of your research. (This is less crucial in the case of journals with specific focuses, where the readership is comprised of scholars well-versed in a particular field whose appreciation for the reexamination of prevailing assumptions or the plugging of gaps in the scholarship can be safely assumed.) There are a variety of forms this can take, such as a series of new questions your research suggests, or speculation on how what you've found has implications for other areas of scholarship. Just remember that it's unlikely your editors will be as familiar with your particular subject as you are, and explicitly laying out the significance of your findings will help them understand why they should publish your piece.
Remember: you're not only making an argument about your subject; you're making an argument about why your argument matters!