Bad work culture

The work culture is very bad in my project. It's 12 to 13 hours everyday plus weekends. And the problem is many ppl are having their milestone and they are working 24 * 7. Saying no is like you are committing crime. No time to prepare and switch. Please give me some motivation on how can I manage my study time and prepare and come out of this. Cuz of stress I have also started spending more time on youtube