Shawn

If you’ve changed the default admin username for security reasons, publishing posts from your admin account will reveal your new admin username to unscrupulous folk.
You can <a href="http://esdev.net/wordpress-security-tip-dont-post-from-your-admin-account/" rel="nofollow ugc">read more about this on our blog</a>.
When the admin is logged in, Admin Post Reminder displays an unobtrusive reminder; informing the user they’re logged in as the admin.
This lets the admin log out and log back in as an editor or user with lesser permissions before writing or publishing a post.
Normal logged in users will not see the alert.

Admin Post Reminder

You should never publish posts from your admin account. An alert is displayed, informing the user they're logged in as admin and not to write pos …

Tapan Kumer Das

This is a very simple post secure plugin, which lets you secure your post from not logged in user. You can choose your desire category to lock the post.

Secure Post

This is a simple post secure plugin, which let you secure your post from not logged in user. Any logged in user can view your post.

Admin Post Reminder vs Secure Post