Human Brain Being Hijacked

I am totally onboard and understand the concept that we process things using both human brain and caveman brain (not literally of course but the concept makes sense to me).

Example: My human brain (me) wants to exercise regularly but my caveman brain frequently tries to hijack this. I understand it is unhelpful to beat myself up when I give in to my caveman brain, but I don’t want that to become an excuse model in itself where I let myself off the hook all the time.

Do you have any helpful suggestions that don’t require either a) beating myself up or b) continually letting myself off the hook?