The key to be self-employed and be both happy and successful is how you manage uncertainty and how you build networks.

While some self-employment work will be pretty stable, most are going to be peaks and valleys. Celebrate the peaks, but remember to always prepare for the valleys. Weeks or months on end without revenue is a very real possibility.

If you live on little, the valleys aren't going to bother you much. But when you start having to provide for a family, cover a mortgage and so on, it can become stressful quickly. Same goes for the general level of income you plan on earning: when I started working for myself, I was fine with around 30k a year, but now I aim to bill 10k a month. Before you think i'm that well off, keep in mind that I have a family, a wife who bring only a basic level of income and I just spend two months without a paying contract (so a loss of 20k in earnings, plus 4k more in living expences - that's nearly my YEARLY earning target of a decade ago!). I'm fine, but only because I prepared for it. Those two months were stressful, but there was no time for relaxation. I had to work extra hard to get out of that slump.

That being said, I would never go back to a stable job. There's an incredible sense of satisfaction to be the master of your own destiny, and every meal you have you know you have it only because you deserve it.