When going through your inbox of unallocated tasks and actions to decide what you’re going to do next and plan out your day, it’s very likely you’ll be rummaging through an unorganized pile of a week’s worth of droppings that haven’t been fully defined yet. Most of the time they’re going to be the small things like, "read this article", or "call sibling for birthday gift ideas". Although it’s not ideal, it’s okay to have these things floating around in your inbox so long as you take care of them immediately or organize them properly.
Sometimes, however, you’re going to come across a bigger task in your inbox like, "write table of contents for mystery novel we’re working on". That is a much bigger task in your inbox that you might never get done if you’re viewing your inbox incorrectly. Skimming through your inbox trying to find the most convenient thing to do at any given time will cause bigger and more time-sensitive tasks to fall through the cracks.
Your todo list’s inbox isn’t structured to handle priority or scale. It’s merely there to help you drop anything at any time for your organizing pleasure later. If you’re going through it looking for something to do, you’re almost always going to choose the things that are easiest and quickest. However, you should be handling the things in chronological order — in the same order in which you added them in the first place. By that standard, you’ll always be getting things done before they become too outdated.
Think of it like rotating milk; when you buy a new carton of milk, it goes behind the current carton so that the opened one gets used and the new one is still fresh when it runs out. If you blocked the current carton with the newer one and continued to buy milk regularly, that carton in the back will grow so sour it’ll stink up the entire house. Don’t let your tasks become so stale they stink up your entire todo list!
You’re supposed to be choosing your tasks based on what you ought to be doing, not what you feel like doing. You may never feel like calling the bank for sorting out your mortgage, but you know there is a time and place when you ought to be doing it. Your inbox alone has no concept of what you ought to be doing, it only has a concept of what you have yet to organize properly and therefore isn’t the proper location to decide or not decide to do things.
Finally, deciding which tasks to tackle on the fly like this is setting the day up for failure since you’re always going to gravitate toward easier tasks and the more difficult tasks are the ones that should be done at the start of the day. Much like the Bimodal philosophy explained in Cal Newport’s Deep Work, most of your energy and creativity are present in the morning — knocking out the easier tasks during that time is wasting the more valuable energy.
Ultimately, it’s important to organize and allocate your inbox as soon as possible at all times — even though it’ll be necessary to cherry-pick tasks directly sometimes, it’ll always be important to be sure you’re going in order of first appearance and not the order of what looks easy and fun.