when to call it quits and when to keep trucking

I've been self-employed for about two years now and I have to admit that it has been rough. It's something that you don't hear about very often from the newly self-employed. Instead, all you hear are stories of self-reliant joy and success. I wish I could say that I am now rolling in the dough and that my schedule has eased up a bit, but that would be a light fabrication. I'm still working longer hours than I was working at my last corporate job, and I'm still making less. I knew that it would be difficult and that it was going to take a while to get established. It's not like you just print up new business cards and some personalized pens and the customers come rolling in. It takes a while to really nail that market. But how long is too long?

Has my stress level dropped since I started working for myself? Certainly - at least with regards to office politics. But paying the bills is my top concern now and there are months when it seems as though we may not make it. Sometimes I think I should just give it up and go back to work for someone else.

So when is enough enough? When you tire of struggling? When you run out of backup funds? And if and when I do throw in the towel, will I be able to re-adapt to a life of servitude once again, or will I be too cocky and independent from my self-employment experience?