Mark

Adds a simple ‘Post-it’ widget to the Dashboard that allows you to leave yourself or other authors a note. The plugin can be configured and moved around as any other Dashboard widget. It will accept plain text or (sanitized) HTML. Only users with the capability “Edit dashboard” can edit the note.
This simple plugin is based on code from <a href="http://wpengineer.com/add-wordpress-dashboard-widgets/" title="Add WordPress Dashboard widgets" rel="nofollow ugc">WP Engineer</a> and <a href="http://rick.jinlabs.com/2009/02/01/how-add-options-to-your-wordpress-27-dashboard-widgets/" title="How to add options to your WordPress 2.7 Dashboard widgets" rel="nofollow ugc">Ricardo González Castro</a>. Leave your comments <a href="http://ideophone.org/dashboard-post-it/" title="Dashboard Post-it homepage" rel="nofollow ugc">here</a>.
Warning Your notes will be replaced by boilerplate text upon upgrading. Make sure to copy the content somewhere else before you upgrade and then paste it into the new version. Sorry about that!

Dashboard Post-it

Adds a simple 'Post-it' widget to the Dashboard that allows you to leave yourself or other authors a note.

mansurahamed

iworksolo

Use the shortcode [private-user-notes] to any page or anywhere to turn it into a user private note page or section. Users will be able to add private notes there using a rich text editor. The notes are only visible to user himself as it’s private right! 
It also gives user option to print their private notes with a single click.
This could be really useful for membership sites where you might want users to be able to save private note in any page,tab or their profile.
Admin can control who can use this feature and be able to save private note. It provides a plugin settings page under Settings inside dashboard where access settings will be found.
Official Developer: <a href="https://www.fiverr.com/mansurahamed706" rel="nofollow ugc">Mansur Ahamed</a>

Private User Notes

Perfect for my need!

It works!

User-private frontend notes: save, edit, print. Restrict by role/user.

Dashboard Post-it vs Private User Notes