You need to have an honest discussion with your boss. Saying no when they try to give you new assignments will backfire on you. You need to talk to the boss, but it's all in how you present it.

I would not approach it from the angle that working 6-6 is killing you and you just can't take it any more. Rather, I'd approach it from the angle that you find yourself feeling anxious, stressed and out of sorts because you drive yourself so hard that you no longer make time to take care of yourself. Tell your boss that in the past, you made time to cycle after work 3 times per week, but you are such a workaholic that you find you are not making that time anymore, and it's starting to affect you negatively. You really miss it. Now that the sun isn't setting until after 7, and it's warming up, you are really itching to get some exercise for your health and sanity, but it's impossible when you come to work at 6 and don't leave until 6.

See ... you present it like it's YOUR problem, and you are asking your boss for advice ... what do YOU think I could do to change this situation, because I'm afraid if I don't make time for myself to get some exercise and take care of myself, I am going to burn out. I love my job, I love doing it well, but I know I need to take care of myself at the same time and am having trouble doing that.

It wouldn't help to cite some articles that you've read recently about the importance of finding a balance between work and personal life. Try these:
http://www.worklifebalance.com/workl...cedefined.html
http://www.businessweek.com/1996/38/b34931.htm
http://en.wikipedia.org/wiki/Work-life_balance
http://www.intelihealth.com/IH/ihtIH...=dmtHMSContent

I learned one thing a long time ago ... if I eat lunch at my desk, it won't take long for "them" to expect me to eat lunch at my desk. If I go to the cafeteria, THAT will be the anomoly. When I took the job that I currently have, I made the decision to NEVER eat at my desk unless it could absolutely not be helped. I leave my desk every single day, whether it's to eat or take a walk around the building. I take the bus to work. That limits how late I can stay, because if I miss that last bus, I'm stuck. (And nobody needs to know what time the "last bus" really leaves -- it's not like anyone's going to look it up.) You know what I'm saying? Sometimes we create our own problems.

Hey, how about this, too? Why don't you see if anyone else in your office rides? If so, start a fun biking group of coworkers. One day a week, you all leave at a reasonable hour and go for a ride. Even if they don't bike at the same level as you, it would be fun, you can coach them along, and you'd also now have others who share your desire to balance work and wellness!

Good luck.