Something that might help is writing things down. For example, if you had a notebook where you wrote down things that you had figured out, every time you came to a conclusion, and any details that might help you remember why you came to that conclusion. Then, whenever you encounter a problem you can read over the notes in the notebook from a variety of topics, and see if any of them match. Also, if you keep it updated frequently then when you go to write something down that would be another opportunity to review the notebook and see if anything matches something else that's bothering you.
Or if physically writing things in a notebook isn't something you want to do, sending yourself an email could work in a similar way.
In general, I've found that writing things down helps with remembering things.
If it's worth saying, but not worth its own post, then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should start on Monday, and end on Sunday.
4. Unflag the two options "Notify me of new top level comments on this article" and "