Oh! ilovetochat! Sounds just like my day today!!!
I'm sure this won't make you feel better, but you've helped me realise I'm not the only one/on my own!
My DS1 (2.2) is usually a little dote, but was asked three times today to stay away from the bowl covered in clingfilm which has the bread dough proving in it. I found him crouching over it no more than seconds after the last warning, two holes poked through the film and into the dough.
I was furious (all down to lack of sleep, and that's not his fault ) and marched him into his bedroom, closing the door behind him.
I felt so guilty, and calmed myself down and went into him and we had a chat, hug and kiss. His little sorry face makes me melt (and feel like a bad Mummy).
To top it all off, DH told me it was my fault for tempting him with the bowl of dough being placed where he could get at it!!!
I know when I'm super-tired I have much less patience, but I find taking a step back, a deep breath, and silently counting to 10 (don't usually get past 4 or 5) really helps, as silly as it sounds. He's still only a baby, I'm the adult.
I'm not sure if this is helping, but I just want you to know you're not alone.