Short answer
Because understanding and behaviour are driven by different processes. Many reactions fire quickly and automatically, while understanding is a slower, conscious process that often switches on after the reaction. Research shows that intentions explain only part of actual behaviour.
Key points
- There is a measurable gap between intention and action.
- Automatic reactions outrun conscious analysis.
- Change requires working with the trigger moment, not only with explanation.
The intention–behaviour gap
Psychology calls it the intention–behaviour gap. Research reviews show that even strong intentions translate into action far from always. This is not weakness of character but a property of how behaviour works.
Fast and slow processes
A popular framework distinguishes fast automatic thinking from slow deliberate thinking. A recurring reaction usually belongs to the first; understanding to the second. That is why you can know exactly what is happening and still react the old way.
Inner resistance
Sometimes a pattern protects you from something: judgement, uncertainty, conflict. Until that function is noticed, understanding meets resistance — and loses.
Questions
No. Understanding is an important first step. It is just often not enough when the reaction fires before it.
No. The “situation → interpretation → reaction” chain is a working frame, not a universal law. It helps you see where repetition begins.