whooooooooooo nice replies cant read them all :) ...
anyhow, as as engineer I understand what you are talking about. I have same problems.
#1 Solution ( that works for me ) : HAVE SOME FREE TIME for yourself. I do this my simply getting up early ( some days around 5:00am ), then do great training ( walk, running, martial arts, swimming, dog walk...). Then healthy breakfast and you are ready to go, energy for all day. Good sleep, friends ( NO WAY TO DEVELOP WITHOUT FAMILY&FRIENDS ), and important thing is to RELAX sometimes.. Daily spend min 45mins in nature and always remember to look at the sky&stars&moon...
And don't waste time on PC. Get the work done and simply fuck off from it :) forget the games, the movies, the web..
all you need is love ^_^