Yes, it's ok to submit your own stuff. If you get to the point where you've submitted 20 things and none of them got any upvotes, though, you may want to start to be more selective.

I'll second this. If you feel it is fitting for HN, then it's perfectly fine to submit it yourself.

There are no rules against that, and if you put in the work to write a thought-provoking piece, it deserves attention.

No gods. Click the 'New' link at the top of the screen.