to be honest mate 3 applications for a driving job is a very small amount......I'd imagine the average amount of applications from the first application to actually getting the job is much higher than 3.
this is why you shouldn't beat yourself up about it too much mate, very few people actually get the job 1st 2nd or even third time!......look at the amount of people you are up against.........all in different situations with different qualities which would make them perfect for the job in their own way yet some poor people have to pick what could be as little as 1 person out of a pool of thousands to have the job! that is a lot of disappointed people.
It took me 7 applications before i got in and some of those i did not even get past the paper sift yet further along the stage someone saw me fit to get the job!......i asked myself why i wasn't fit for the job at the first application but the only conclusion i came to was it was just a mixture of experience, timing, luck, circumstance and people with better applications.
just keep jumping through the hoops that you are told to and you WILL get there, it just might not be straight away....just think your applications will only get better.....patience buddy