"Exercise only in the morning" is terrible advice. I cannot wake up one second earlier than I must in order to get to work on time. If I followed that advice, I would never exercise. The best advice is to find time to exercise every day, no matter what time that may be.
I'm not saying I don't exercise. I just do it in the evening after work, when I feel it provides a couple of benefits. (1) I do it consistently every day, because I feel more "up to it" at that time. (2) I feel that it helps relieve the stress of my work day, since focusing on my form and nothing else is almost meditative to me.
I just feel that making people think it's somehow better to exercise only in the morning will discourage some people from exercising daily, which I feel is more important than the time of day.
I am the same way. I have trouble falling asleep (will toss and turn for 45 minutes to 2 hours), so I'm loathe to wake up before I absolutely have to, because once I'm asleep, I want to stay that way. As a result, I just schedule my day so that I work 8 hours, then do everything else. It has its downsides, but its better than everything else I've tried.
Exercise in the evenings definitely amps me up and makes things worse, but in the mornings I often end up with a "OK, done my work for the day, now I deserve to relax" feeling that is very hard to shake. In addition to getting up on time, feeling light-headed and sick due to lack of sleep while exercising, etc.
I think you've sort of touched on a separate issue. I'm a night owl but find it far easier to wake up in the mornings if I'm excited for something. Often I wake up earlier on the weekends than on work days because I'm not particularly looking forward to going to work.
