Please don't be upset. And please don't worry.
These are my mock results from December 2017:
Religious Education: 5
English Language: 8
Mathematics: 4
Biology: 6
Chemistry: 4
Physics: 5
French: 6
ICT: A
These are my actual GCSE results from June 2018:
Religious Education: 8
English Language: 8
Mathematics: 7
Biology: 8
Chemistry: 7
Physics: 7
French: 8
ICT: A*
Drama: 6
English Literature (sat this in June 2017): 7
I too, was extremely upset with my mock results. Words cannot express how disheartened and demotivated I was when I opened that piece of paper and saw the absolutely awful grades (my awful may be different from your awful) - I wanted to be a doctor (hence why these grades were awful), I had big dreams and aspirations - and when I saw that, I crumbled. But it was a big shock, and for a good reason, because it kicked me right into gear and made me realise that nothing comes easily. After those results, I revised relatively regularly - for maybe an hour or two each night, doing my notes in biology and chemistry (I kinda ignored physics until a few days before the exam but please don't do that because I was on the lower bound for grade 7, I actually got a grade 6 but then it got remarked because I was 1 mark off and I got pushed up to a 7).
Like I said, please don't panic. I was in the exact same position this time last year, and I've never been filled with so much joy and relief in my life as I was when I opened my actual GCSE results. The hard work will pay off, you just have to put it in now, and you'll get there. I promise!
I wish you the very best of luck. If you ever want to talk, message me!