Hey so I'm a Latin student in y13 (actually had my first Latin A-Level exam yesterday!!) and I know that feeling really well of feeling that you haven't managed your time right. I would say not to panic too much about any subject going less well than you'd hoped in the mock - in my y12 mock for English Lit I got a C overall, with a D in one paper, but I was predicted an A because it's such a cumulative subject and I just hadn't figured out the technique yet, and I actually got an A* in my y13 mock!!! There's still so much time for everything to change.
The main thing I would recommend is that you take advantage of this summer. The reality is that you will probably feel a bit burnt out after your mocks but by late July/August you could probably force yourself to achieve something. If you were to, for example, re-learn all your vocab and the translations of your set texts, that probably wouldn't take too long after having recently learnt them for these mocks, even if you didn't do it very thoroughly. Can I ask what exam board you are doing? I have quizlets for all the AS and Verse vocab for OCR if you want them.
The other thing I would say is that unfortunately the content only gets harder in y13, but the y12 stuff then gets comparatively easier. I feel so much more relaxed about my y12 set texts now I've done the y13 ones and they seem much more manageable. But also by the time you get to your exams you will have a really good idea of the magnitude of what you need to get done so it shouldn't be too overwhelming, as long as you learn from this experience and time your revision slightly more strategically.
My last tip would be if you find out that some of your learnt set texts aren't coming up/aren't coming up in their entirety in your y13 mock, learn them anyway over the Christmas holidays because it will make it so much faster to recap them when the actual exams come round. Good luck!