Focus on tasty primal foods -- and don't look back
I don't know if I'm especially flexible, but it was easy for me to go from SAD to vegan cold turkey and then to go low carb/high fat meat primal. I just focus more on the new stuff that I get to eat and don't think about "what I'm giving up."
I picked up a bunch of nice veggie dishes when I was vegan that I still enjoy today -- ratatouille, green smoothies, dark chocolate, coconut milk kefir, nuts, brussel sprouts, etc.
Now that I am primal I love soft boiled eggs, lamb curries, bulletproof coffee, butter on everything, hollandaise sauce, liver and onions, etc.