Stop, Snap, Switch

I'm interested in learning about the process by which people can change their default automatic thoughts as discussed in the episode 85: Jim Kwik | How to Unlock Your Brain's Secret Superpowers and the clip Overcoming Automatic Negative Thoughts. From what I understand, the process of change involves paying attention to your thoughts, noticing when they aren't aligned with the future you want, and choosing to challenge and replace those thoughts. For example, if you have the default thought "I'm not smart enough" and want to become a more confident person, you would acknowledge the thought, challenge it by saying "No, that's a lie," and replace it with "Actually, I'm very smart, and I choose to believe I'm smart." Is that enough over time to weaken the connections of the original thought and establish the new thought as the default? How does that happen? Is it through long-term repetition, or by adding another thought immediately after the one you wish to erase or replace?