I started riding to work a little over a year ago. I was not in terrible condition, but certainly not athletic. For the first few weeks the 10 mile round trip would kick my butt. I could realy feel my legs after those rides. The weather prevented me from riding daily, but that was probably a good thing as it gave my body some time to recover. Every week it gets a little easier. If the ride to work is to long right now, start with some easy rides a few days a week after work. Try to ride a little farther each time. If you have specific problem with what is stopping you from riding, post them here. There is a good chance that whatever is hurting or bothering you has been experienced by others. Don't worry about how long it takes. If you hit some head wind, you'll be slower, but who cares... just enjoy being outside. Listen to your body. Some days I feel stronger than other. Those days I'll push myself harder. If I have a day that I don't feel as good, I just ride easier. Either way I am getting outside, I am working my body, and I am saving a nice amount of money by not taking my car.
It has been a little over a year since I started riding my bike to work. I now find the 10 mile ride (round trip) a breeze most of the time. Now I find my self reguarly going for a fun "quick" 20 to 30 mile ride. LAst year a major goal was to ride a local event and go 33 miles. I did that and felt realy good about my achievement. This year I wanted to ride futher and now I can easily ride 33 mile rides a few days in a row. It takes a little time, but you will see progress. At first you may not notice it, but after a while you'll realize that the ride gets easier and stops being a struggle.
Happy riding,
André