I got a big truck (diesel, about 14 mpg)
I have a big SUV (gas, about 22 mpg)
I would drive a bit less. Simple as that.
Since diesel will be higher probably than gas, I would have hubby take my SUV to work, I get the truck but only drive when necessary in one big trip to get all needed and home. I would plan any recreational driving to planned events etc.
I would mow a bit less. (I mow ALOT with the farm

)
I probably wouldn't bush hog certain areas.
Don't know if I would make hay or not off the acres. price of hay would jump very high for people. Probably just down enough hay for my own farm.
I would still take my vacations and save money everywhere else I could in my life. Nothing will stop me from my camping trips...although instead of 3 separate weeks at the beach, I would probably go once and STAY longer
what gets me is the cost of all the other products. high gas means high everything else. So it isn't gas that would just nail ya, it is all the high prices. I would definitely become more reliant on farm grown foods (I am there right now but still do buy alot in stores). Just buy less and eat more of the same on the farm.
things would change a bit but I wouldn't go down....it would hurt, but it isn't going to take me out of the game!