When I'm planning out my weekly workouts, I always try to make sure I get a run or workout in on Monday. Why Mondays? Starting out the week with a run sets the tone and pattern for the rest of the week. You're beginning the week the way you want the rest of it to go.
Running on Monday also helps if you know you want to get in a certain number of runs during the week. It means that you're starting the week with one already under your belt. Feeling that sense of accomplishment so early in the week gives you a boost of motivation and confidence that you can take through the week.
Also, social events are less likely to pop up on a Monday evening, so your evening running plans are unlikely to get derailed by a last-minute invitation to dinner. You can make it to the gym without feeling like you're missing out on something. And, let's face it, Mondays can be stressful! Running is a great stress reliever and a good way to help you deal with the challenges of a new week. Hope you have a great run today!