Do as much as it takes or as little sets you can get away with. Some days it takes more. Some days you just won't get there cause of distractions or diet / water consideration, rest, stress...etc
i can usually tell if it's not going well by the second exercise. And i will ditch the whole gd thing and do calfs, abs and rear delts. I can always get pump there. or find a milf to eye molest while in doing some stair master. Sometimes I get on the stair master for like 10-15 mins and i get back in the mode and return to by workout.