The reason why our Limiting Beliefs are so hard to change is due to a term called Cognitive Dissonance.

What this essentially means is that we feel a massive amount of discomfort when our beliefs, ideas, and values are challenged. Therefore, we will change how we interpret situations so that our beliefs stay intact. For example, if someone holds the Limiting Belief that they are ugly and another person tells them “You look good today” then the person who has the “I’m ugly” belief will say something like “Oh they just said that to be nice” so that their interpretation is consistent with what they already believe, and their belief stays intact.