You should try to get a little sun routinely, even if it means buying one of those home UV lamps (just don't burn yourself, start reasonably). Also take some vitamins and get some exercise. Other than the higher risk of depression, I know of no other reason why being a night owl should be bad for you, other than if you are a night owl, and you are always trying to be awake when you don't feel awake, and trying to sleep when you don't feel like sleeping. IOW, listen to your body.
I have been a night owl since high school, since puberty really. I just never 'feel' quite human during daylight hours, especially morning daylight hours. No matter what I do, go to bed at 10pm every night, nothing, I just never feel 'right' in the day. Whenever I have tried to hold down a morning-day schedule, I am always feeling sluggish, and I am far more likely to nod off at work, school, while driving, etc.
I do far better in the evening day hours and at night, and after a number of failed attempts to hold a day schedule, I've just found it foolish to try.