Things I don't care about & don't have control over.
The least important but most difficult category to master.
All items that occurred in the past are either category 3 or 4.
Items which occur in the future are to be viewed either as entertainment or ignored/forgotten.
First master category 2 before focusing on this category.
Many of these items are to be simply ignored then forgotten about; you have more important things to do with your time/energy. Life is short.
Being upset, worrying, or dwelling about these items is prohibited; if your emotions are justified then the item is category 3, not 4.
The instant I categorize an item as category 4 is the time I (begin to) let go of it.
For me this category started out as a trash can, but it ended up as a black hole. To continue the analogy, things can get out of a trash can, trash must be emptied, trash eventually starts to smell. However, nothing can leave a black hole.
Previously, I had tried to decide how to handle category 4 items. How much time and effort do I spend? How do I decide? Now I simply don't handle them, I ignore them. If they require my attention, then they're probably not category 4.
I used to catch myself justifying my neurotic perfectionism by thinking "If I can learn from this past event (3 or 4) then I'll avoid it in the future, thus thinking about it is an investment in my future. How else am I to improve? I must think about this in order to make progress." So I'd then counter that thought by reminding myself "I've been thinking about that event on and off for years, and haven't made any real progress. All I'm doing is dwelling on it, and thus wasting time and energy. I'm reinforcing a bad habit of dwelling on things that don't matter and can't be changed (4)."
So category 4 was eliminated and its 'space' allocated to the other categories. I began with a pie chart I visualized which had 25% allocated for each of the 4 categories, but now I had only 3 categories and decided to grant the extra 'allocation' to category 1, it was now 50%. Mastering category 4 was difficult for me because it's simply not in my nature to let go of things.
I perform a single action on all category 4 items: "This item no longer exists." Thus it's not really a category like the others, it's more of an action.
I once considered jury duty as category 4. I later decided I do care and do have control (if I really want it). I considered using the control by cheating (1), or not using the control and just doing the service (2). I didn't want to cheat since I feel it is a duty, one that I actually believe in and support (in other words I didn't care enough), so I chose category 2 for this item and sure enough I was called to jury duty not long after. Of course it happened while I was very busy with work. I thought I was in a difficult situation (3), but realized I had some control (1). I used that control, which was court rules and exemption paperwork provided by my employer, in order to reschedule the jury duty so the situation was no longer urgent (2).
Considering the purchase of a lottery ticket (X) and actually winning (Y) are two different items:
Y is impossible unless X occurs first. If X occurs, then Y is changed from impossible to highly unlikely.
X is category 1 or 2, not 4, because you have control over it. X is not category 4 (or 3) until it's in the past; until after it's been accomplished or chosen not to be accomplished. If it's a small amount of money you spent then you don't care, thus it's category 4.
Y, however, is category 3 or 4 and remains as such; you never have control over Y. One could claim you have a small amount of control over Y, since it can not happen unless X occurs first. However, Y is not about actions & abilities, it's about luck. Now should you perform other actions such as cheating the lottery system (1 or 2) then the effects of luck have been reduced/removed, thus you gain control and Y becomes category 1 or 2.