I've learned this the hard way. In a physical office, I might have a better idea if he was having personal problems that impacted his job performance. I could watch as he performed his duties and make sure he wasn't wasting time. From thousands of miles away, though, I can only cajole him to finish projects before the due date. I'm currently working with him to implement time management and project tracking tools, so I have a better idea of his daily accomplishments.
Scheduling is very important to working unsupervised.
Sometimes I have a ton of flexibility - I can succumb to the temptations. Other days I put in 12 hours to get an important project done or help out my co-workers. But I'm sure to let the people I work with know what I'm up to on any given day. We have a lot of trust in our employees and we know that real life happens. You might be interrupted but we trust that you're still getting the job done.