I know people who pride themselves on their ability to do regular 60+ hour weeks. I've been one of them even - wearing the 'workaholic' badge like a right of passage, the hard core willing to make the sacrifices. And at crunch times, knowing you can kick up a gear and do this for a sustained period is good. Muscles waste away unless you use them, after all. But when the long hours become the norm, something is wrong. It's not work, or the market, or this project, or your manager - it's you. You are becoming addicted to work, failing to take control and ignoring the other demands on your life.
Like any habit, burnout hours creep in gradually, then bind you tightly. If it feels odd leaving your desk and going home at seven, that's a warning sign. Being productive requires balance in your life - emotional, physical, spiritual and intellectual. If you are only satisfying a few of your needs, and exposing yourself to a limited range of experiences and input, then your output will be similarly restricted. You can't live on a monotonous diet and expect there to be no side-effects.
The burnout cycle occurs when your performance starts to tail off, and you compensate with longer hours. Longer hours lead to lower productivity, which you combat with yet longer hours. Before long, you are the lights on/lights off person, topping and tailing at the start and end of each day. It's a lonely position and eventually you will give up or fail. The trick is to recognize when this is happening to you, to take responsibility and to stop it.
Managers are only interested in output, not hours. They also recognize a burning martyr. It may feel like you are earning brownie points, but unless the results are there, it's more likely you are coming across as disorganized. Instead, take a deep breath, and ask for help. It's likely that with prioritization, delegation, a few productivity changes, and some training you can get out on time. This will break the burnout cycle. Own the problem, fix it and you'll find renewed energy and passion for your work.