Long Haul Flight Soon - Nervous - help!?

Hi i have a long haul flight soon in about 3 weeks and i am getting a bit nervous about it. I have been on long hauls before (sydney>los angeles>chicago) and (sydney>singapore>london) but that was about 6 years ago. i am travelling from Sydney to Frankfurt, via Brisbane and Singapore. Then im taking a train (9hrs) to Nantes, outside of paris. I have flown lots of small flights, such as SYD-BNE and SYD-MEL and SYD-AKL but i am nervous about getting sick on the plane, which my mum tells me people dont get sick on planes anymore. when i get nervous i kind of get a bit nausea but what should i do to calm down?