Was supposed to be 3 up, 3 x 3 MP w/ 1 mile recovery between and 3 down for total of 17. RHR was stupid high when I woke up and was just downright exhausted. Finally got out around 1 and it was hot and humid (82 with DP of 68). There was a pretty nasty headwind on the way out on the canal (which helped the heat a little but hindered in other ways obv). Got to the last 3 mile block and my body and brain just said no. Think I'm fighting something off. Frustrated but better to call it and not need longer to recover running myself into the ground. John agreed.