maloner:
What if you receive Communion after knowingly fasting for only, say, 30 minutes ?
Do you mean saying to yourself, “Well, this Church law is dumb and I only wish to keep it for 30 minutes, so that’s what I’ll do.” If you mean this, I agree with another poster above, it is grave.
If, however, you mean that you were helping your child with a sippy cup of orange juice and for some reason you ended up thoughtlessly sipping some to encourage your child or some such thing, so that your fasting time is cut short or your fasting is imperfect, well, I don’t think this is of the same type. Is it still nonetheless grave (to receive after accidentally having an imperfect fast)?
I think it can well be grave, but if, say, you think it was an hour but cannot be positive when the sippy cup incident took place, then I think it might not be grave.
I worry that people may tie themselves up in knots and end up not receiving Jesus when really they ought receive. I think some people can get sort of scrupulous with regard to the Eucharistic fast.
Whatever else one does, be sure to prepare for communion each time, praying before hand, mentally doing an inventory, etc.