Strict paleo is very hard. Don't beat yourself up over yogurt, especially if you went for the plain kind. It's not like you fell face down into a bag of potato chips or pizza. Many cravings can be avoided by eating something fatty instead. You may have wanted the sweetness of yogurt (even the plain kind breaks down into sugar). Sweet cravings can be headed-off by eating something salty or drinking a little pickle juice.

For me, just sourcing naturally raised and wild food and avoiding processing is hard enough, without also trying to live without butter and wine. Which is why I'm a paleo/primal-tweaker But you'll certainly be able to follow strict paleo eventually if you want it enough. Good luck.