This is the single most important part of the dispatch career. You will have challenges at every step in your career. You have to be stubborn and have a never say die attitude. There will be days where you ask yourself why the fock did I get myself into this business? The working hours, workload, the pay and the inherent instability of the airline industry are enough to make you question the decision to make dispatching a career.
I would say that more people are not able to handle the dispatch lifestyle than the dispatch aptitude but the two are so interconnected that in a certain sense those that fail out of dispatch school are the ones that were weeded out early who could not live the dispatch lifestyle. Indeed, you can say that it takes someone with a personality geared toward toward the career to have an aptitude for it. If you do not have a particular passion, attitude and personality for dispatching then this will be manifested in your performance in dispatch school.
While we all learn at different speeds, the dispatch material is not so challenging that it takes someone with a special mind to learn it. But it is a fast paced job and the dispatch schools all try to get you used to that fact by throwing all the material at you in a short period of time. If you can't learn a large amount of material in a short period of time you will not be able to make it as a dispatcher. Even if you get through the training, once the training wheels come off you are on your own in a sink or swim environment. The earlier you figure it out is better so you don't put a lot of time into a wasted effort.