Enjoy it !
Pat,
First of all you have to enjoy what you are doing, it's not compulsory to learn to fly, it's not cheap and it's your hard earned cash so make sure you enjoy it.
From my own experience, I've been flying all kinds of aircraft since I was very young, Hangliders as a kid on the hills in the Yorkshire Dales, Microlights, Pitts Specials RV's etc and I can tell you that a thorough walk around and check is the most important thing I do to this day and something which I learnt very early on in my flying career. I once saw a very very experienced Hanglider Pilot pick up his glider and set off running over the edge of a hill only to find out very quickly that he'd forgotten to "clip in" - he was very very lucky, the hill was shallow and he managed to run it off, but had he been on a ramp take-off on a mountain or cliff edge, he wouldn't be here now - that was pure complacency on his part!
Pilots do become complacent, at all levels and it's easy and quick to kick a tyre or two to satisfy yourself, but you owe it to yourself and of course your passengers because you have a duty of care to them so keep up to your high level of pre-flight checks, no matter how long it takes because trust me, one day it might just save your life.
Maths was never my strongest subject, in fact, I'm convinced I'm mathematically dyslexic, mmm! and I too remember the panic when asked to do some number juggling but somehow I managed to get through it.
It's never been an issue since my learning days because I can take my own time and I'm not under too much pressure, and there's always a whole bundle of IT to help me if I need it!
Sack the instructor! I once did! I had an instructor who in my view was completely mental !; Swearing, banging the top of the panel, sighing every other minute, in fact just about every bad manner you could imagine. I was about 9 or 10 hours at the time, did two with this instructor, got out of the plane and sacked him on the spot -it was a great feeling to see his mouth drop! There's no excuse for foul language or any other form of discouragement for that matter when teaching.
On a good point, I have flown with some fantastic instructors, people who really make you feel that you are doing a great job when you are and help you when you're not, and in turn you improve because most of it is about confidence, and that's what you're lacking, so move him on and you will move up quicker than you could imagine.
Good luck and keep going, it's worth it.
Martin