If there is one thing that a good solo run provides, it's time to think. I've had some amazing long runs by myself where I've been able to find focus around a problem at work, a relationship, or a multitude of other of life's challenges.
"If you don't have answers to your problems after a four-hour run, you ain't getting them." ~ Christopher McDougall
When I first started running, a lot of what I thought about was the act of running itself. But as time went by, running became automatic. I no longer think about running at all when I'm out putting in some miles. The running part is like breathing – it's just happening. Left foot, right foot, repeat.
Runners talk of "the flow". The times when I'm not thinking about running at all are the times when I'm getting the most out of running. That flow state, for me at least, is when the running is just a background task that some deep part of my brain is handling.
When I'm in that mode I can either ponder some other problem that I've been facing, or just shut down my brain almost entirely and just be out there.
Some days I can remember everything about a run – details are captured and stored over the timeline of the run and I can replay them in my mind like annotations on a GPS track. Other days I get back to the house after a run and I barely remember where I even ran, let alone what happened along the way.
Which is best? Both. Running gives me the time and space to think or not to think, depending on what I need at that point in my day. I can run to clear my mind and solve a problem at work, or I can run and clear my mind to escape that same problem.