Your Stuff > Discussions is the place to go to follow your topics and topics in which you've posted...
You can also use widgets effectively, but if you want to go directly to a list of threads you've participated in, and see which ones have been updated with new content, the Discussions link is the most efficient way (i.e., using fewest clicks) of doing that.
I get "Not Found: The item does not exist it may have been deleted" when I do this.
This is the link you need to follow (which you might want to bookmark):
That's where you'll be led if you follow the instructions above. Everyone's Discussions page is accessible in this way. Mine, for example, is here:
If you find that your Discussions page is unavailable, please inform the Hosts about it by starting a new topic here: