It sounds like you have not properly set limits. If you work....say 24 hours a week and the clock goes off saying you've worked 24 but there's still sooooo much work to do, do you know what you should do? You should shut off your computer, leave your office room/table/whatever and stop working. If someone from work calls, let it go to voicemail and pick up on Monday.
I learned early in my full time career to do this. One job, during the interview with the CEO, he asked me "what hours do you work?". I remember putting it through the algorithms in my brain. I could sound like a hero and tell him I work 60 hours a week or I get the job done and don't worry about hours. No.....I said "8 to 5 monday to friday". This later saved me when a department head, trying to one up the rest of the managers decided that all salary employees should "give" an hour a day on them to the company. So work an extra hour. Nope. I was called into an executive's office who was besides herself that I get there at 8 and leave at 5. "That's what I said I'd work to the CEO".
Anyways, you HAVE to set your own limits. If you don't, you'll be one of those 80 hour a week people who will still be laid off when business drops.