There is a joke: "Project managers are people that believe 9 women can give birth to one baby in a month." It is your professional responsibility to set realistic expectations. Going all out and working a 80+ hr. week is mentally exhausting, which in software development leads to more bugs than genuine progress. In France since 2000, the legal work week is 35 hours, and anything over that is overtime, allowed up to 220 hrs. per year. http://www.time.com/time/world/article/0,8599,1873245,00.html
The Puritanical idea that hard work leads to success is a myth. Success is setting expectations and then going beyond them. Talk with your boss and bluntly ask them: "Do you want to meet deadlines with a low quality product and burnt out workers, or have a high quality product with fully engaged workers?" If they say they want quality, speed, and low cost, they are delusional. It's the iron triangle, choose 2. If they won't listen, it's time to update your resume and start looking. Don't waste your life spending 40+ hrs. a week in a miserable environment.