Headbanging, shouting screaming, frustrated and sometimes walk away mummy

Well I often have bad mummy moments, but luckily they are always surrounded by loving hugs and fun too. Today my 11 month old daughter banged her head trying to escape the 'nappy changing mummy' and I felt pretty rubbish whilst hugging her after lots of sobbing tears. Mostly I'm a bad mummy when my impatient frustrated needs clash with my baby, often if she's throwing her food of her highchair and for the 500th thousand time I'm bending down to wipe and collect it or sweep it. Now we are practicing handing the food to mummy that she doesn't want. I generally feel like a horrible grotesque monster if I ever 'lose it' and raise my voice which on occassion has made my baby girl cry. Sometimes I walk away and leave her in these moments to gain some space! And calmly walk back to her and begin again.