I know exactly what you mean. The employee thing often gets to me. I try to remember that, when I was an employee, I was never as motivated as the boss either, and I just expect less from them...but I still don't put up with the real tossers!
A lot of the time, I keep going because it won't get done otherwise, and bills won't get paid. Not the best situation sometimes, but I do enjoy what I do, which helps. If I start to get p1ssed off with certain types of work, I stop taking it on. I got fed up with trimming hedges long ago, so don't do that any more. I also got fed up of being asked by customers to overprune trees so that there's a fraction more light in their kitchen, or there are fewer leaves to sweep up come Autumn
Over the years, I've pulled out of working in people's gardens for the most part.
Sometimes, I look for other types of work I've never done before, and take on low risk little jobs here and there, just to see if we can do it profitably. Variety, and all that..!
For me as well, my stuff is seasonal. It's a lot quieter in Summer, but I work hard in winter. Over the year, I do an average amount of work, but it's all crammed into the winter months. For example, I did 7 days a week for February, March and most of April, but I probably won't do much in May. I find it more interesting than 40 hrs per week each and every week, and it breaks up the year.
The hardest bit is when you've not got much paying work on, but there are lots of maintenance jobs to do. It's too easy to take it too easy and grind to a total halt. If that happens to me, I'm in trouble, because I find it very hard to get going again.
I try not to take too much notice of the profit and loss, because it sometimes seems like I'm working for nothing. Sounds like a recipe for disaster, but you can tie yourself in knots worrying about not making enough money. I find that if I don't think about it too much (within reason), it's less of a problem, and I'm happier..
Finally, I think of some of the jobs I had to do when I was an employee, really cr@p jobs, jobs we had to do because we had no choice...like picking up twigs in a field for two days, strimming round fence posts on the side of the M1 .. or the office jobs which are too painful to think about. It's never as bad as that, nor will it ever be, and that always cheers me up.