Anal Sex

It seems like majority of guys like anal or at least want to try it and I’ve just never had interest in doing it. I find it gross and to be frank, I would really like to keep my asshole tight and small. Literally thinking of having to do it someday makes me cry because of my anxiety. But I feel like I’ll let down my future partners and they’ll always resent me if I say I don’t want to do it. How do I warm myself up mentally to the idea of anal?