What is the effect of a judicial decision making retroactive effect?

"In general, judicial decisions are given retroactive effect. [Citation.] Exceptions to the general rule are rare and usually occur when prospective application is essential to preclude injustice. [Citation.] ' "[T]he hardship on parties who would be saddled with an unjust precedent if the overruling were not made retroactive, ordinarily outweighs any hardship on those who acted under the old rule or any benefits that might be derived from limiting the new rule to prospective operation." ' [Citation.]" (Wilson v. Tri-City Hospital Dist., supra, 221 Cal.App.3d at p. 450, 270 Cal.Rptr. 436, fn. omitted.)