I've trained myself to 'just say yes' to co-workers who cajole me into ducking out for a lunchtime run. I know from experience that I almost never regret the runs that I do, but I almost always regret the ones that I skip. And when my co-workers are weak or overwhelmed, I do the same for them. Its an informal deal we've worked out. Sort of a get-off-your-butt support group. Go find enablers. It's harder to skip a run if you know others are heading out and expecting you to join them.