Tamar217,
I wouldn't get too worried at failing grading, or using it as an indicator for your ultimate aptitude for flying.
Military aviation is tremendously demanding and the training has a finite amount of money and time to train some one to operate a high performance dynamically unstable helicopter at night in appalling weather from a small flight deck off the back end of a frigate. It is a very different type of flying from airlines and they push people very hard from the outset to ensure only the best potential pilots get the vast amounts of money spent on them.
However, military aviation is a very very small percentage of the overall flying community.
Likewise, in the early stages of a PPL, most people find the going tough. If you take significantly more than 45 hours to complete the PPL however, I would seriously look at the viability of becoming a professional pilot. Taking 15 hours more at PPL, then CPL, then IR with addition costs for re-sits can very quickly mount up financially and would be quickly noticed by prospective employers.
Only you will know whether or not pursuing the dream is viable because at the end of the day some very fine gems can be hewn from the roughest looking rocks. There is no substitute for the learning gained from experience and so 200 hours down the line you may well achieve a good standard as a commercial licenced instrument rated pilot.
However, my simple advice is that if you still look back after a rough, demanding, poor performance and hard working flight and still want to get back in the aircraft at the first available opportunity, the flying bug has well and truly bitten. Whether you fly for fun as a PPL or professionally is however the much harder decision that only you can make.
Regards
Obs cop