Just remember Oxford isn't everything. It's good to set yourself a goal, at a young age as well, but you've also got to be realistic. it is your responsibility to aim for a realistic goal that you know you can achieve. GCSE's aren't the end of the world, they are just a stepping stone to A-Levels which are far more important in the eyes of universities. It was also my impression that Grade 9's were the equivalent of an A^ and only a tiny percentage of candidates would achieve such a grade- a Grade 8 is essentially the equivalent of a normal A* I thought. It's good to strive for perfection sometimes but it is also helpful to fail too; it really is the only way to learn. Instead of worrying about a decision you'll make years from now focus on your GCSE's. Only take latin if you genuinely believe you would enjoy doing it, don't do it if you think it will be a chore. It's like any choice in life, only do it if you think you will enjoy it.