When you are creating or modifying something – a new furniture arrangement, a new aspect of your routine, a new way you want to approach particular social situations – design for not only the expected use but also for several possible other conditions if major variables switch to other settings than what you predict.
Prepare yourself for comfortably rolling with the changes.
There is a great discussion of this principle in How Buildings Learn: What Happens After They're Built by Stewart Brand (a book which informs about a much broader range of thinking than merely the architectural!) on page 178. He says "All buildings are predictions. All predictions are wrong." I'll tone it down just a hair:
All plans are predictions.
No predictions are 100% perfect.
By preparing yourself for imperfection and envisioning reasonable responses to the most likely alternate scenarios, you'll reduce your stress and optimize your results.
Here's an example:
Over the past few years I kept reading about treadmill desks and thinking "Wow, that might work great for me." I finally reached a point where I was ready to try it. Instead of just making a plan to switch to the first one I heard about, I thought about some possible alternate scenarios to "Everything goes as I hope and I love it."
Alternate scenario #1: "I don't love it."
Influence on my plan: Find a way to invest less money on the experiment so it's not too painful if it doesn't work out. (I have more time than money. If you're the opposite, ordering the fancy pre-made solution could work for you if you are satisfied with the company's return policy).
Alternative scenario #2: "I totally love it and want it permanently, but it takes up too much space and disrupts our use of the room which serves as my office/guestroom/Joe's desk area."
Influence on my plan: Explore ways to rearrange that room which still allow for all the functions we currently use it for instead of assuming I need to leave my current workspace where it is.
Alternative scenario #3: "I like it, but my body takes a long time to adjust to working while standing."
Influence on my plan: Create 'infrastructure' to support taking care of myself physically. Continue using a rest reminder (I use TimeOut on the Mac) to give myself time away from keyboard and treadmill. Make a nice seating area near enough to my walking desk that I can step off for a few minutes and rest my body while writing on paper or reading a book or doing something else that doesn't require the computer.
Even a short brainstorming sprint on what else is fairly likely to happen besides your favorite prediction will allow you to plan better and build solutions which can accommodate a variety of futures without breaking.