the staple run

This is my running equivalent of 'session beer': 6 miles at conversational pace. It's my staple run, which means I do it 4-5 times per week. Since time doesn't matter (these are 'recovery' runs) I usually don't wear my watch, but always assumed I was maintaining a fairly consistent pace. Apparently not. Out of curiosity I recorded my splits this morning: 7:25, 7:25, 7:03, 7:10, 6:55, 6:42
Oi... well I think one or both of these are happening to some degree: 1) I'm running a consistent effort, which is only loosely correlated to a consistent pace. 2) The observer effect. Not to be confused with the uncertainty principle. I have my watch on, and I keep checking the effing thing, and I observe slow miles, which alters my pace, and I check it again, and faster miles improve my mood, etc.
Okay no more watch during the staple run.