Beliefs are interrelated and come together in a thing called one’s "philosophy of life". There are broad supporting beliefs, like "the world is unsafe" or "I'm threatened if I think I don't have self worth" and then there are derivative or determined beliefs that one makes up to support the foundational beliefs. And then there are derivatives of the derivatives and so forth. In a sense the lower broader levels of beliefs are like pillars that hold up a table. If you remove the pillars the table (i.e. derived beliefs) collapses for lack of support.
Therefore, one will find that not each belief needs to be corrected, as some will disappear when the pillars are changed. Getting as close to the foundation as possible and dealing with those beliefs produces the greatest improvement of the overall belief system compared to trying to deal with each of the the thousands and thousands of derivative beliefs.
The beliefs are habits of thinking, that automatically happen, even when we might not be conscious of them.
When one wants to correct an old belief that is harmful, one must replace it with a new belief, that is somehow justified with arguments and perhaps evidence that it is true. It does little good to say a statement over and over if the mind says "I don't believe it." Therefore, every new belief must be based on truth or be possibly true.
You could say that there are big beliefs and little beliefs and that changing the big beliefs have alot more impact. For instance, if someone studies the reasons for and then understands thoroughly the belief, which is actually also a tautology (i.e mathematically true and equal): Each person (I) does the best he (I) can at the time give the current limits of his (my) awareness [aka knowledge, beliefs]. If something is done incorrectly, with the wrong result, then it is not the fault of the person, but due simply to his lack of awareness. The solution therefore is to cure the lack of awareness (learn completely). Of course, if the effort is not worth it, one would not do it, as in correcting or "informing" another.
Once a person fully understands after studying it what the above actually means, several of the key beliefs that are based on erroneous teachings and learning from the culture will simply disappear. Some of these are:
"I'm bad because..."
"I'm not worthy because..."
Anger (other than if a severe attack is occurring which demands action)
But, I've noticed that few do the work to understand this foundational construct, as they want to go to the intermediate or little belief to correct it - but that is impossible if the underline big belief contradicts those.
The best investment of one's time is in addressing the foundational beliefs. The one that I found was the most impactful was the Barksdale materials. You might wish to link into the resource page and then use the free e-books.