As others have said, careful revision and consolidation of weak topics will ensure you're at your best for Year 11. I would look at the Math Advanced syllabus (as much as it is quite vague... -_-) or Year 11 textbooks such as Cambridge and compare this to any textbooks for Year 10 so that this can indicate the topics you have to improve on which will also be in the Year 11 course. The reason for using textbooks to compare is a bit more self explanatory I suppose - you don't want to end up using the Year 11 textbooks for Year 10 revision, but rather for the actual coursework once you've mastered the basics. Don't revise the unnecessary things (if you were in 5.3 Maths) such as Circle Geometry or Inverse Functions, as CG was in the old syllabus for 3U and Inverse Functions is in the new syllabus but for Extension 1. Revising pointlessly like this will decrease the time that you have to revise for the more major topics (e.g. Algebra, Trig) so it could be of best interest to keep this in mind. Make sure to study effectively, but also because it's the holidays and you're in the bridge between Year 10 and 11, have fun and enjoy your holidays as you'll be studying a bit harder for the next 2 years.
Hope this helps.
Edit: With what I said about the unnecessary things, everything in Year 10 which you learn is assumed knowledge for Year 11/12. However, the chances you will have to use some of these topics are very minimal. I guess one example of this is maximum and minimum problems in Year 12 where you may have to use Similar Triangles to solve a problem. Such a topic like this is assessed in Year 10 but is not directly taught in the Advanced course.