This takes great will power on the part of the Dominant , but I have found it to help with first time anal, be well lubed and warmed up from fingers on anus rubbing not penetrating, The Dom places the tip of the head of his cock to your asshole, then doesn't move except to make small circles as he grasps the base, He doesn't push at all, He waits til you start to push back onto Him, never moving until you beg him to. This should help with the anxiety you feel as you can take as much as you can and get accustomed to being penetrated .at your own pace.