Just a note to say thank you for all your help. You've been such a great teacher and Maths has now become one of my favourite subjects. I really appreciate for everything.
You can write in this way:
Dear XXX,
Thanks for your guidance!I started to like maths now because you teach me maths.
Best Wishes,
XXX
It is a thank you card,no need to write 令我感到好榮幸.