If you sit in a minecart using CTRL and Left Click on a mac, you can get in a "drive" the minecart, but you can't get out. I have tried CTRL and Left Click, I have tried breaking the mine cart, everything. The only solution is for someone else to break the minecart from beneath you. You are esentially stuck evertime you get into a mine cart. It also says 'CTRL and Left Click to dismount" like you are riding a horse, which is odd.