I can totally relate to this. It's really hard to explain this to my family, because there's so little information about this online. Especially since I'm from a non-English speaking country, there's no information about DSPD at all, and most of my family members don't understand English. So I really have no way to prove them that it's really a disorder, not something I can change. I get really pissed off when someone tells me that it's just a bad habit, because it's not. I've tried to switch to a ''normal'' sleep schedule a lot of times, even skipping nights sleep and forcing myself to go to sleep at an earlier hour, but it all fails eventually in a day or two when I get back to going to sleep when I naturally need to.