I'm a professional developer for two years now, going into my third year. What I noticed since week one, and i never had an issue with at school or university, is that I can't really work (i.e. program) for 5 days a week, 8 hours a day.
My maximum productive time is about 4 hours a day. This is more than enough to keep up with my colleagues. If I have to do more work, let's say for a bugfix or a critical feature, I almost immediately get headaches which can last for a week or more.
Obviously I'm very unhappy about it. I used to read books in the evenings, learn stuff, now can't even listen to music some days.
Do you have any advice on this? Colleagues and friends i consulted either can't relate to it, or just in a very general sense ("Some days are though"). I'm serious enough to cancel my software developer career if I can't find a remedy some time soon, even though I love to program.
: I actually keep track of my time with RescueTime, trying to limit my "productive time".