Being able to articulate your decision rationale can make all the difference in your confidence (and others' confidence!) Interestingly, most people stumble when asked for the rationale behind why they made the decisions they did.
Rationale is the third part of the D.A.R.T. Method® of deliberate planning.
Sometimes, decision rationale is not more sophisticated than, "It just felt right," or, "Everyone else seemed to be on the same page about it," or, "That's how we've always done it."
Needless to say, these are pretty weak.
Decision rationale is linking the decision to why making that choice in particular gets you closer to stated goals, or the mission of an initiative. Why this and not something else? Can you articulate trade-offs and implications of the decision? Can you explained the reasoning in a way that makes sense to someone who wasn't in the room?
How to define decision rationale
First, name your goal that the decision is being made in service of. We're trying to accomplish something, right?
Second, state how the decision gets you closer to (or achieves outright) the stated goals.
Third, as a best practice, acknowledge the other ways you could have gone, and why this decision in this case makes the most sense. This way, you are showing that you are aware that this isn't a slam-dunk, obvious decision, and that there might even be detractors, but that you have thoughtful responses to why going in another direction wasn't optimal.
For some, it can take some time to define decision rationale well - succinctly, effectively. It can be a thought-provoking exercise that helps to build confidence in decisions over time.