Most people who didn't get through didn't pass the selection - pass all the tests (maths, english, capacity etc) and you're in with a good shout. Obviously you have to convince of your motivation etc in the interview. However, part of showing motivation and resilience is bouncing back from setback and succeeding next time round after putting in a lot of work on the areas that let you down.
Often those who get in second or third time round go on to be the best as they value what they have more and have a greater hunger.