Beyond that, probably the biggest single evolution was in my relationship to the work itself. In the early months and years I loved being able to go heads down on a project without ever worrying about the politics of the project or the organization: I was there to get the thing done. However, I am the kind of guy who cares about his work. Eventually I found this same experience to be dissatisfying. I felt that I was abandoning my children into a hostile corporate world with no one to look after them.
Moreover, as a freelancer you have much less influence over the product and the process. You're a hired gun. Sure, you can do a great job and collect a good paycheck, but if you love what you do it can be frustrating to have extremely limited input into decisions outside the scope of your contract.
Back to the author's very excellent point, I also found the management of benefits and finances to go from a source of engagement to just another hassle. When you are setting up your system, it's fun. When you are executing it, and occasionally screwing it up (taxes!), it's just another headache.