The best thing to do is to stop looking back. The time in the past, let it stay in the past. You can't wind back the clock, work hard and play hard. Make a comprehensive plan of what you need to do for the rest of the holidays and stick to it. Don't start self-blaming yourself because it will just be endless and extremely unproductive. I think it is much more important to catch up then to get ahead-because if your foundations are not strong, you will struggle very strongly when school term starts. Do one thing at a time, and don't overwhelm yourself.
The following extract on how to make a timetable from my senior study guide would be of help in this situation, for the full guide feel free to check outhttp://community.boredofstudies.org/128/preliminary-hsc/317056/how-excel-senior-year-studies-yr-11-12-a.html :
HOW TO ORGANISE YOUR STUDY TIMETABLE:
I think the best way to make a time table is to make it flexible, whether you have a to-do list by day or organise your day into relaxation and 1 hour long study sessions, do what works for you. There are a few things you should make sure to include in your timetable/to do list to make it effective
1)Always be realistic-don't assign excessive amount of work that you cannot achieved in the designated amount of time you have set aside for yourself
2)Make sure you are flexible-so you can make adjustments to your timetable when extra-curricular and any other unforseen circumstances comes up.
3)Make sure you are studying at times optimal to your concentration and alertness level. Don't assign studying at night if you can't concentrate during that time
4)Include social activities, work commitments, relaxation time into your timetable-a balanced lifestyle is essential for long term academic success
5)Make sure you follow your timetable as closely as possible and try not to have too many carry over tasks to add onto tomorrow's workload. With lots of trial and error, you will find a way of organising time that you will feel comfortable with and which works for you
Best of luck-do your best and don't look back
You can do it as long as you have enough faith in yourself!