Thanks for the ideas and replies. I actually love riding my bike to and from work. I always feel better when I bike to work vs. driving.

It just seems that 10 hours seems to be some kind of cut-off for me, where my motivation/energy to do anything after that (aside from drive home) is close to nil. If I work 8 hours, I generally look forward to the ride home and enjoy it. If I work 8-10 hours, I might feel tired, but I usually am happy after I ride for a bit. After a 10-12 hour day, I feel spent - physically, psychologically, intellectually... It is hard for me to summon up motivation for the ride home.

I feel very safe on my commute, that is not a concern. Lights might be a factor. I have a Nightrider Lumina 650 on my handlebars now and I was going to use another light on my helmet after daylight savings. The discussion about lights made me think of another possible factor. I have a thyroid disorder and have taken thyroid hormone for about 10 years. One thing I have noticed since taking the thyroid hormone is that my night vision is not as good. I also need to get a new pair of glasses & I've been procrastinating about doing this. My new prescription is just a tiny bit stronger than my current one. I have terrible vision and am pretty much blind without glasses.

As far as creatine goes, I don't know. I'm female and the the possibility of losing hair and retaining more water doesn't seem very appealing. Since taking thyroid hormone, I have found that I can build muscle easily if I work out regularly and eat well. If I don't work out a lot or eat well, than I put on fat easily...

Maybe I'll try a smaller cup of coffee closer to the ride home if I am tired. I will also experiment with getting new glasses and a stronger light.