Why can't I just not do it?

I got up early enough to go for a run this morning, but to be honest , I just CBA, 'I'll run tonight' I thought.
There had been a sprinkling of snow overnight, but that wasn't the reason, 170 run/bike/swim/walk miles in 2 weeks, now that was the reason, tired legs. Anyway I was to finish work at 4:30, plenty of time for a run. Needless to say, it was well gone 5 before I finished work so I as Jed needed a walk I went for a dogjog with him. It was more stop than start today, Jed enjoyed snuffling around in the snow, so I decided on a fartlek session and ran hard between Jed's stops. Was a nice session under a bight starry sky.
After tea I went for a swim, just the thing for tired legs. It's a while since I've been to the 8-9 O'clock session, it was nice, not too many people. I set off with breast stroke cos I'm rubbish at it, then swam a few lengths crawl without using my legs, then no arms and left arm only right arm only and did a couple of tumble turns, they were not great but it was fun trying.
The whole purpose of the session was to take it easy, but when I was doing full stroke front crawl, I could not resist chasing the other swimmers. Why can't I just ignore them and do my own thing. So it ended up quite a bit more tiring than planned.
Run 3.7 miles
Swim 1 mile
Total for day 14= 4.7 miles