Hate to be a party pooper, but Jetstar is essentially the budget arm of QANTAS. I would have no hesitation on getting on a Qantas aircraft tomorrow, but due to savings at the moment my next few flights are on Jetstar. Anyway aircraft wings are designed to have wing flex in them. Check out a picture of a 777 on the ground, and then just after rotation.
Also this might help:
http://www.flightglobal.com/blogs/fl...mb-476x237.jpg
As for ways to help, try and keep your mind occupied elsewhere. Enjoy a film/book/magazine, and just try telling yourself that the aircraft is more than capable of handling the turbulence.