You have 3 options Karen;
1. Stop posting from this moment on. This will give you the option of returning to the site without having to register again at a later date, and you'll still maintain your post count.
2. Admin can make your account inactive. This is the same as above except you can't log in to the site until an admin makes your account active again, you would have to make a guest post requesting such.
3. Admin can delete your account. This is permanent and can't be undone, your previous posts will remain until the next prune.
If you have specific reasons, pertaining to the site, why you would like to discontinue your registration please pm me the details. If the reasons are personal to you, please let me know which option you would prefer.
HTH
