JetBlue TrueBlue - What happens if I don't use my return flight?

Sorry, new to jetblue. I won't be using my return flight on my OAK to BOS trip. What happens to the fare? Will it go into a credit where I will have to pay a fee to reuse it? Whats the fee? Also will I lose the 40 bux i already spent on upgrading to EML? Thanks!

If you cancel you will get all of your fare - 100 into a credit that is good for 1 year. If you call up Jetblue they will credit you for the 40$ eml fees also (it does not get done automatically ).