Change will be uncomfortable, but change should not make you miserable.
False Assumption 1: you should make drastic changes & lifestyle shifts.
You do not need to go from 0-100. Incorporate small, incremental shifts in your routine until they become habit. Instead of a daily gym routine right off the bat, start with committing to 2 days a week until that is a part of your non-negotiables for several weeks before adding another day. If you cannot imagine doing it for the rest of your life, it's likely not sustainable. START SMALL!
False Assumption 2: changes should happen all at once.
ONE THING AT A TIME! Often motivation has us wanting to do the most all at once, but when that motivation inevitably wears off, we realize how unsustainable these new protocols were. Start with the big things that will make the biggest impact: movement, sleep, hydration, and nutrition. Pick a habit or two and start there. Add more as each new habit becomes routine.
False Assumption 3: you need to deprive yourself to the extreme.
"Changing" does require a shift in your habits so maybe you have to 'reduce' certain things in your life, but you don't need to completely abandon things that make you happy - everything in moderation (and if it is something that is not supporting your health, slow, incremental reduction is best).
False Assumption 4: perfection at all times is required.
Expecting perfection often leads to feeling like a failure when we inevitably miss a protocol for the day, but by realizing that perfection isn't realistic, when those difficult days do come around, you will choose to still control what you can and know that you did the best you could without the guilt.
False Assumption 5: feeling miserable is inevitable.
Uncomfortable? Yes. Miserable? No. Anything outside of your norm will feel uncomfortable, but in order to change a circumstance in your life, you and your habits need to evolve. If protocols you've implemented make you feel miserable, you're likely changing too much at once.
False Assumption 6: progress is clear, linear, & quick.
Every day might be and feel wildly different. How our bodies and minds function is dependent on so many factors that it is impossible to control it all. Control what you can and monitor trends over time to assess if you're moving in the right direction. CHANGE TAKES TIME! Do not expect a quick fix to be sustainable.