I mean, there are a lot of important lessons you learn when you have a "project from hell", so my reasoning is that the project better be small, so at least the price will be low.
I had done a large number of smaller projects and several mid-sized projects, as well as one very large one by the time I started working on this though, so it's not as though I was green behind the ears or something.
Maybe the morale should be 'know when to walk'. And I should have walked long before I did. The violence is what made the coin drop for me, it was a realization clear as day, 'I'm being abused here'.
Suddenly the veil came off. After that quitting was relatively easy.
They'd always said that. Then at midway, suddenly "we need the money, and there is this client willing to pay if we make it such and such. It shouldn't be that hard eh? I know you can do it". On and on.
Till this day, if anyone says "I know you can do it", my alert level would increase.
To me, what made it easy for me to quit, was the fact that my boss didn't not want to spend any money on sales to sell the finished product, when all this while he had been spending money on the development of the product. For all the talk of "I am being most loyal to the company" and "I sacrificed a lot for the company", he hesitated on doing the final push.
As naive as I was, I suddenly discovered it would be stupid for me to stay. That made it easy.