Although The Work for many people seems to be remarkably effective in allowing knots to unravel, there are also particular issues for each of us that seem especially sticky.
In my own experience, these beliefs seem to be the ones I have invested a great deal of energy to reinforce over longer periods of time. I have created a whole network of beliefs which support each other and hold each other up. I have found and collected lots of evidence for them. I have a strong identity made up by this network of beliefs. I know how to shoot down any beliefs that don't seem to match this network of beliefs. And so on.
But these too seem to unravel over time, one thread at a time.