I totally get it, I have that same contrarian instinct.

I have to reframe someone telling me "you should do X healthy thing" as "you should look into X healthy thing and see if it interests you/if there's really a good reason to do it", and then if I do my own research/reasoning, sometimes I can get my brain on board.

Basically, I have to trick myself into thinking it's my own idea. Very silly, but hey, it's how I started eating more vegetables and drinking more water, at least.