Overwhelmed / angry

Hi everyone, me name is Melissa and I live in Belgium. I am being treated by an endocrinologist at a hospital and just had an appointment at the hospitals dietitian.
It's urgent I lose weight so I have to start with a 1000 calory a day, PSMF diet.
I have a big wedding to go to this friday. She adviced me to begin right after that event.
But I am feeling extremely overwhelmed. I am scared of being hungry and irritable because june is pretty much the worst time of year at my job. Stress levels are pretty high. I work with teenagers who are in the middle of exams.

Can anyone relate? How does being in such an extreme deficit influence your daily life?