heart and soul

heart and soul (http://definr.com/heart and soul)

     n : the choicest or most essential or most vital part of some
         idea or experience: "the gist of the prosecutor's
         argument"; "the heart and soul of the Republican Party";
         "the nub of the story" [syn: kernel, substance, core,
          center, essence, gist, heart, inwardness, marrow,
          meat, nub, pith, sum, nitty-gritty]
     adv : with complete faith; "she was with him heart and soul" [syn:
            body and soul]