Click on your username, you'll get to your profile page. Under your user name you'll see "show posts." Click there.
If they're topics you started, you can follow Larrabee's directions and then click 'topics'.
For posts you liked (with the
), click on 'likes given'.
If there's a post that I know I'll need in the future, I'll bookmark it in my browser so I can easily find it when I need it.