JetBlue airlines have laid their policies carefully on the website. You can check them and it is said that you should know about the policy before booking your flight. It is not healthy having last minute flights and disputes over Jetblue cancellation policy.
Now, if Jetblue cancels the flight, you get a full refund and if you have cancelled the flight on your end, you get the refund according to the refund policy mentioned on the website.
Make sure that you know about the policy otherwise, you might feel cheated and distressed. The policies can’t be changed under any circumstances. Hence, take care while booking your flight.