I definitely believe most of us have our cortisol being released at wrong times, and we have a lot more difficulty changing our sleep times. It is so common for us to not fall asleep until sunrise. I think I have DSPS. I usually go to bed around 3 am, then a few days later it's 6 am. It stays around sunrise for days, but then it will get later and later, and I'll be forced to push forward. So I will go around the clock until I get to 11 pm, but it won't stay and goes to 3-6 am. My main problem is falling asleep. I don't have much problem with staying asleep. I am bad about waking if I have not gotten a good 9 hours.
Sometimes I feel that I've tried my best for many days, with little result. When I struggle to change my sleep, I usually feel worse for days. However, twice I've had some multi-day event coming up and I was very motivated to change my schedule for it. I succeeded pretty well both times. I don't feel like I was lazy before, when I tried and couldn't change, but this helps show me that it's possible, when I try very hard, because I want it more than anything else.
Then the problem is, I will usually not maintain the new schedule. I am not sure I can maintain it without help from someone who lives with me. Once I have woken up in the morning a few times, after the difficult days, it starts feeling good. I would love to see how I feel after consistently waking in the morning for 4 weeks or 4 months. I think it would help me.
Soon I will be changing my schedule again. I am not looking forward to the first 2 or 3 days. If I don't have enough days to go forward around the clock, or if I can't because I have obligations, then I usually have to deprive myself of sleep for 2 or 3 days, getting about half my normal sleep. Without getting too little sleep, I won't succeed. When depriving myself of sleep, I have to use mild stimulants like chocolate to keep myself awake. I have to be very careful of all the foods, drinks, supplements, everything. Especially in the 5 hours before bedtime. Some supplements are wake producing and need to be first thing in the morning. I take melatonin for the first 3 days. I would like to take it more, but I get problems. I have to get out in the sun multiple times, and I think it's necessary to skip sunglasses for better effect. I try not to get blue light for hours before bed. For whatever time is my goal for wakeup, I have a clock lamp that simulates sunrise which helps. It helps me a lot if someone can wake me up - if not, I need 2 very loud alarm clocks. It helps me to have someone else around, who falls asleep when I am supposed to. I also do more physical activity (except the first days with sleep deprivation), so I am tired at bedtime.