If it feels like getting ready for your viva is a lot of pressure, or if you feel like you already have a lot of priorities, then start small.
Do one thing. Find thirty minutes to read and commit to it, rather than rush and hurry to get it done. Make a small window in your busy life to make some notes. Ask a friend to spare half an hour to listen and ask questions.
If it feels like there is no time you still have to prep. Ask for help. Get support from friends and family to free you up to do the necessary work for getting ready.
If you only have a little time you still won’t need a lot to get ready for the viva.