Don't worry too much. It will almost certainly never be like driving your car, even when you are very current. Many years ago when I flew piston singles I could drag one out of the hangar, fire it up and fly off in almost as many minutes as it has taken me to write this piece. But my planning started as I got out of bed and continued on my drive to the club. Was it windy? What was the cloudbase? Fuel requirements - Visibility - Thermals - wave (unlikely) - winch cable position - local ATC etc. were all considered. I had, I suppose 300 hours in singles by this time and a 1,000 hours gliding. But as no time did I ever think of it like a car. And whenever I went somewhere new, I used to plan and prepare for the transit and arrival, just like you probably do now for every flight. That's the learning process.
For now, you have to trust your instructor's judgement and take a certain amount of comfort in that 1. You won't be put up for test until you are ready and 2. The test will be just that, a test. To pass, you will prove to the examiner that you can fly to the required standard. And even once you pass, you'll still find that there are many things which you are uncertain about. So you'll still be getting advice from instructors and others, all the time you are flying.
PM