ignore the 'it's too late now comments'... they're trolls and are clearly trying to be funny but in fact, it's just discouraging to us needing motivation. Set a certain target of topics you have to complete for the day (the night before).. you can set a time target (e.g. 6 hours tomorrow), however, it's always seemed a little daunting to me when I woke up and realised i had to do six hours.
Start off by creating a list of all the subjects, how many chapters are in each unit and how long each chapter will take. Ik this will seem like an extremely boring task to do, but trust me it helps knowing how much revision you have left against time, so you can be time-efficient.
I discovered this a few days ago:
https://www.reddit.com/r/GCSE/comments/47kdr2/revision_megathread_past_papers_google_docs/ ) and have been finding it really useful.
For maths, I did my gcse last year in it and did well. Seriously the only way to get better at maths is to practise, practise and practise... its the best way, and, tbh, unless you're a genius, its the only way. I also highly recommend you do past papers as well (but only AFTER you've revised!/ as your going along). Also for some topics i really didnt understand (like graphs of trigonometrical equations- WTF WAS THAT LOL- use exam solutions). they're really useful and have a website which covers basically everything from each major exam board
Ik you need motivation atm, and so does everyone who has exams in a month. But remember, motivation will only get you to start it once but discipline will help you be consistent and strive for that. the only way TO achieve that is by setting yourself a certain target every day, as mentioned before, and strictly follow it.
Revision can be a pain in the ass literally all the time but only the first two minutes of revision are the hardest, however after that trust me, you'll most likely forget your even putting effort in.
Anyway, i hope you do well in your exams, but it's time for me to actually put my words into action, haha. good luck and i hope i helped