How often do you have emergencies? Seems to me that if your life is going sideways, paying the penalty to get money out of your 401k would be worthwhile; but I

How often do you have emergencies? Seems to me that if your life is going sideways, paying the penalty to get money out of your 401k would be worthwhile; but I expect that my life generally won't go sideways, so the extra percentage of income is more likely to be a benefit than the potential penalty is to be a detriment.