What is the burden to establish an abuse of discretion on appeal?

burden to establish an abuse of discretion has occurred. (Cf. Blank v. Kirwan (1985) 39 Cal.3d 311, 318.) " '[T]he showing on appeal is wholly insufficient if it presents a state of facts . . . which . . . merely affords an opportunity for a difference of opinion. An appellate tribunal is neither authorized nor warranted in substituting its judgment for the judgment of the trial judge.' " (In re Marriage of Varner (1997) 55 Cal.App.4th 128, 138.)