Since early childhood, I've never been very successful at living a day-adapted schedule. Going to bed at dawn and waking up at noon is the natural rhythm I've always fallen into, given the chance. I sleep just fine during the day, and have never needed blackout curtains. And I do get sun exposure for Vitamin D; I just get mine in the afternoon.
I finally chose self-employment so I could dictate my own hours, and have been contentedly nocturnal for the last few years. I've always seen a noticeable improvement in my mental health whenever I've been on a night schedule, and in the last three years I've seen a big difference--I've finally been able to make certain changes in my life for the better.
That said, day-people (who are the majority) really do suffer when they have to work night shifts for very long. Just as I've always struggled when keeping a day schedule (and all the while performing at a sub-par level and being extremely stressed out), day people have the same difficulty on a night schedule. Either way, it can be extremely stressful. But if you're a night person, and that comes easily to you, and your ability to think and work and function is better on a night schedule--there's no real need to change.
Is it working for you? That's the most important question to ask yourself. Because you'll get plenty of people telling you that no, it can't possibly work, and that if you think your idiosyncratic way of doing things is really working you're deluded, or broken, or just plain wrong. Screw that noise. Is it working for you?