My thoughts regarding people having difficulites with aspects of the PPL training are:
1) you will perform infinitely better if you chill out a bit in yourself. I can remember doing my training that at the start I was so tense that my instructor sometimes couldnt use the rudder, so rigidly pressed against the pedals were my feet. I was making no progress whatsoever, with each small error making me more and more wound up and hence perform even worse. When I did my first solo however things changed dramatically. I felt like all the pressure was off me, and the subsequent improvement in my flying was so great that I finished off the PPL in chilled out ease.
In my case certainly my problems were psychological rather than due to a lack off aptitude and I think that is the case for the majority of people who get frustrated with their progress.
2) Your instructor can make a huge difference. I had a couple of different ones during my ppl, one of which was completely useless, every hour spent with him was a waste of time and money, in fact Im almost sure that he was deliberately holding things back to make me do more hours and thus pay him more money. The guy was getting me more and more wound up and things finally came to a head when during circuit training I blew my top and let fly with a torrent of abuse at him, landed the plane and ended the flight. My next flight with a different instructor was a joy, and the change of instructor enabled me to gt my first solo in and never look back.
So in essence, dont put pressure on yourself, focus on being proud of what you have learny already rather than on what you cant master and be prepared to chuck in your instructor if they are crap, which a good many of them are.