Hi there

That is the most common problem people have these days.  If you want to make a serious career in a field then you should first go through your aptitude and interest in a field.  If you like to teach but get a job of a salesman than you would feel uneasiness in your workplace but if a job is according to your aptitude and interest then the time would be no problem, I saw people doing there jobs for almost 14 to 16 hours.  So select a career according to your interests and aptitude and then give full time to it, you will be a satisfied man soon.