Not quite true, BigGrecian
We cannot and do not suspend guys from training (chopped in old speak!) simply based on personality. Likewise, a good personality is no guarantee of passing either.
If a student has the skills and the capacity (especially capacity), he is more likely to pass. I have know some truely great guys who have fallen by the wayside because they could not cope with flying a fast jet in a complex and changing scenario. On the other hand, there have been a couple of complete kn*bs who have passed due purely to their handling skills and ability.
I guess that personality comes under Officer Qualities and we cannot suspend for lack of said until they reach the front-line.