To reduce decision space, you need to look at a) how large is the pool of pending decisions, b) how many options are available per decision, and c) how clearly are the options defined. Below are some tricks that work for me:
Pool of Pending Decisions: represents the complete universe of undecided things, including both conscious and subconscious decisions you need to make. The larger the pool, the more overwhelmed you feel. You wouldn't even know where to begin and might end up chopping away at some of the easy decisions to give yourself the illusion of making progress.
- Deleting decisions: It took me a while to realize that it's OK to decide that you're not going to make a decision about something. The decision to "delete" is still an explicit decision and clears the pool.
- Any-choice-is-valid decisions: Sometimes you're happy with any outcome as long as there is a quick outcome. In cases where all options on the table are above a certain threshold, you can reduce the time/energy it takes to make the decision. Any decision works.
- Automating routine decisions: Removing decisions from your everyday routine is extremely liberating. You can "program" your optimal morning routine once (after thinking hard about it) and then follow it like a robot.
If you've reduced the pool of pending decisions, then at this point all the things you're spending time thinking about are important, so you're already ahead of the curve.
- Cap maximum options: it helps to explicitly decide the maximum number of allowed options per decision. You need to fight the temptation to consider "all possible" options. Looking at all options creates decision paralysis. There is a reason why Apple gives you only a few options of the type of iPhone you can buy.
- Clearly define each option: it's extremely important to define the options very clearly. Clearly defining a limited number of top options for any given decision is 90% of the work in individual decision making.
The system I have is far from perfect and is likely to evolve over time. I'm really curious to learn about how other people deal with decision fatigue.