There is a self sabotaging side to humans that yearns to fall back into habits or comfort, even if our intellectual self hates that old self.
Goals are a great thing to have, but there's always that risk of seeing them as an "end point." When that happens, we can want to treat the entire journey as having a beginning and an end, instead of letting go of one lifestyle and starting a new one.
Ask yourself why, and be brutally honest.
What are you trying to avoid (consciously or subconsciously) that has led to that desire to want to fall back into old unhelpful habits?
What isn't working right now?
What's causing you to feel like you're white-knuckling through the day and needing to "zone out" or disassociate?
You have to find out what it is and then accept that it isn't serving you. Surround yourself with people who will continue to help lift you up to be your best self.
Stop avoiding the negative feelings by falling into comfort (old unhealthy lifestyle). You're only harming yourself in the end, even if it feels soothing in the moment.
Be OK with being uncomfortable.
-The Wonder Vegan