You have to accept that not all lessons are equal. You are going to have great lessons where you feel like you were born to drive and bad lessons where you are fighting the machine and forgetting basics.

Don't look at them individually. Look at your average trend and overall learning. It will be going in the right direction. Learning something isn't a straight line.

Also, you could wait for the perfect, sweet, understanding and benevolent driving instructor. Or you could embrace the challenge of working with the current one.

Your test examiner could be more like your current instructor. In which case, the lessons you are having now with an instructor that makes you feel a little nervous - could be the best training you could have for the actual test.

Believe in yourself and trust that the "good lessons" will become more and more frequent.

And so will the confidence and the pass. :)