How often your work gets published is somewhat out of your control, but you can control how often it gets rejected. Set an ambitious yearly goal for the number of rejections you hope to receive and be unabashed in pursuing it. Resolve to submit your work widely and accumulate “no thank yous” from the most prestigious agents, editors, publishers, and publications you can find. Striving for rejection will get you in the habit of putting yourself out there, help you grow a thicker skin, and stop you from self-rejecting by failing to submit your work in the first place.
If one of your submissions gets accepted for publication, don’t be deterred! Dust yourself off, write and polish another piece, and see if you can get it turned down from someplace even better.