Actually, the hard part was not giving up by the second interval.

Ran 3 x 1-mile intervals for a total of 7 miles.  1% treadmill incline.

1 mile warm-up @ 6.5 mph (9'14")
1 mile interval @ 8.5 mph (7'04") – tough, but manageable
0.5 mile recovery @ 6.5 mph
1 mile interval @ 8.5 mph – exhausting, but made it.
0.5 mile recovery @ 6.5 mph
1 mile interval @ 8.5 mph – like the push at the end of a 5k race.  For a full mile.
0.5 mile cool down @ 6.5 mph
0.5 mile cool down @ 6.6 mph
0.5 mile cool down @ 6.7 mph
0.5 mile cool down @ 6.8 mph

Gee, that wasn't so bad after all.  My body just doesn't have much will to run hard these days.