I don't let anything about the biz stress me out (deadlines, technical glitches, failed PPC campaigns, whatever). I don't rattle easily. (I was even called "unflappable" in a letter of recommendation once.)
But here's what does cause stress for me:
spending more time at work than with my husband. This applies to both my full-time job and also my time in front of the PC when I get home.
Even if we're both in the home office, if I'm working on my online biz, I'm "in another world" as far as he is concerned.
He's very supportive. He never complains. But I still feel HE should be my top priority.
To relieve this stress/guilt, I often delay my biz activities until he's busy with something by himself (working on the car or whatever).
The result of all this is that I have very limited time--between the full-time job and the "hubby quality time"--to spend on my home biz. So I need to make the most out of the time I have, and get SERIOUS with prioritizing and planning. But that's a different topic.