+1 on what JonhathenB said. At every stage you will struggle to practice anything- they are trying to test your innate abilities here, not your learnt abilities.
I thought i failed at every stage, and now that i'm waiting for my stage 3 results, i still think that i've failed!
No part of the application process is easy and you should not expect it to- alledgedly they had 55,000 applicants last year and they took 160 to college, of which 1/3 will fail, of the remainder 1/5 will fail to validate! So out of 55,000 people about 90 will actually become air traffic controllers.