Putting in the training miles one knows there will be long stretches of running by oneself. It can be a good time to collect thoughts, work through problems, or just focus on style, pace, and form. But this is about running with a friend. There’s a lot in favor of running with someone. Here’s a few reasons: no matter the weather, your friend will show up so you should, too; you can run at a “conversational” pace which keeps the pace a bit slower than you might have run, which is good for longer runs; the run seems to go by quicker, since you are chatting as you go; your friend can watch you and give you tips on your form; you can congratulate each other at the end of the run, giving fist bumps or whatever. I know there are plenty of other reasons, but these are just a few.