Our history as humans from thousands of years ago, is still having an effect on how our brains are working.
Thousands of years ago, when we met a big bad wolf in the forest, we had not time to think. So for the purpose of saving our life, our basic brain structures, our amygdala were helping to shut down all other brain functions including our thinking processes, our sexual desires our need for approval, our creativity, and made us fight or flight, run for our lives or try to fight off the danger. The fear for the wild beast had successfully triggered fear and an appropriate reaction for our survival. Since we were not very fast or strong comparing to the beasts preying on us, it was best to learn where it was safe and to really go and explore the unknown. Major changes were readily triggering our amygdala, shut down all our higher brain functions and got us ready to run or fight.
Now if we have to sit for this very important test or we face a major change in our life, our amygdala tend still to respond in such a way. We want to lose weight, but diets are difficult, exercising demands time and causes us to have sore muscles initially at least and instead of effectively going towards the change, our fear sets in and we are in a run or fight mood. Our higher brain functions shut down and no change tends to happen.
Now small incremental changes in what we want to achieve, tends to bypass this primitive response. If we start with one snack less per day, we may not lose a lot of weight in the first week, but we see that change is possible without too much effort and we are encouraged to take the next step. Or for exercising, instead of enrolling a program of half an hour for five days a week, which is very likely to fail we then start with doing a few minutes of exercise every day. No trigger of fear, no trigger of amygdala no run or fight response, no shutting down of higher mental functions.