One thing I have found to be of the utmost importance in maintaining a relaxed homeschooling atmosphere, is keeping our schedules as open as possible. Nothing stresses me out more than the pressure to be getting ready and going somewhere all the time.
As much as possible, we stay home. I believe that the simplicity of this is overlooked. Children and mommies alike need lots of time and room to, well, RELAX! And if we are driven by our outside activities, relaxation often turns to frustration.
We were very fortunate to find a piano teacher that even comes to our home to give lessons. Otherwise, we have never had music lessons away from home until this year. We started violin, but as a compromise, I asked our teacher if we could do lessons twice a month instead of every week. Two lessons less a month is a big help.
If you find yourself stressed from outside activities (or little ones who seem frustrated), maybe a schedule overhaul is in order!