PA28 pilot reported descending below the approach minimums during final approach due to night conditions; fatigue; and complacency; as well as not wanting to overshoot the airport.

Narrative

At night; following a long day and a three-hour flight from the north; the weather at ZZZ was reported as OVC015 so I got an IFR clearance for the RNAV Runway XX approach. I was landing straight-in Runway XX. In the final segment leading to the missed approach point; the weather turned out to be fairly clear. I could see the ground and surrounding area. But I could not positively identify the airport; in part because it is offset from the final approach course. Because it was clear; I wasn't focused on the approach minimums and let myself get too low on approach; 400 ft. over the hills; when I should have been higher. I eventually identified the airport and landed uneventfully. But I was 400 - 500 ft. for three miles leading to the airport.I should have stayed above the approach minimums until I had the airport in sight and not started descending just because it turned out to be clear. If I had done a visual/VFR approach; I would have started higher and approached normally; but starting out on the RNAV approach left me lower than usual over the hills and I continued to descend without leveling off. I should have paid more attention to my altimeter and not relied on visual cues; which were leading me to descend lower than I should. Contributing factors were nighttime; fatigue; familiarity with the airport leading to complacency; and the desire to start descending soon so that I did not overshoot the airport. I should have accepted the risk of overshooting the airport and just stayed above minimums until I had the airport positively identified. I should also have used my digital tools better; iPad; to realize I was too low and to help identify the airport. I should also have remembered that this approach specifically notes that there are obstacles; hills; in the visual segment; so I should be extra careful to stay above minimums at night. In the future I will be more conscious that I should only descend below approach minimums when I have positively identified the airport; not just the surrounding area; and overall at night I will be more mindful of my altitude when landing.