Self-employment is really the key. You really have to be in a position to set your own hours.

I had a real shit weekend thanks to a bank error. By Monday, when I got everything resolved, the fire drained, leaving me whipped. So I said fuck it, I'm taking the day off. I can do that.

I also have very little stamina doing law work. I can do all sorts of other shit all day long, but I can only work about two hour blocks at a time max on client matters. So I'll work a little in the morning. A little in the afternoon. Sometimes at night. Make phone calls while I'm lifting, etc.

I've also been doing this long enough to be keen to clients monopolizing my time. The real key is to never meet when the client wants to meet. I know it's kind of dickish, but once you let the client dictate any scheduling, there is a contingent that will think my scheduling and meter is their prerogative. I have to cut the possibility off early. Plus, of they're really serious about my services, they meet when I say.

To put it another way, to pull it off, you really have to control time.