If one develops a habit of meditating on their affirmations, the ideas within the affirmations are more likely to come to mind during an emotional incident and help to regulate behavior towards the desired outcome.

The "coming to mind" of valuable self-regulating ideas is "mindfulness". Yes. It's subjective. That's OK. And yes, it may not work for everyone. People are different and have different ways of reacting and different levels of self-awareness.