Some of the stupidest decisions I made are the ones where I said yes at the moment. I said yes to a deadline without taking the time to check my calendar, and then over the next weeks, it impacted how much sleep I got. It impacted how much of a dick I was to the people around me because of the level of stress. 

A simple: "Let me come back to you a bit later with the decision" would have saved me all that trouble. Because with the break in my enthusiasm, I would have realised that yes, I want to help, but I can't manage that deadline instead can propose one that will lead to a better result and a more healthy situation for me.

Simple things can really mess up weeks of your life. And simple things like taking a break before taking a decision can save weeks of your life too.

This is a first draft of a principle that might end up in a book of the "Service Design Principles" series.