Stressful periods are rare for me, especially since I pick my projects and set my own hours. Recently though I've been setting them too aggressively.
The stress I experience happens when my reach exceeds my grasp -- I get frustrated when projects have to remain undone because there are too many other higher priorities ahead of it. This just means that Erin and I have reached the point where our business has grown too big for the two of us to continue going it alone.