Okla. Stat. tit. 23, § 21

For the breach of an obligation arising from contract, the measure of damages, except where otherwise expressly provided by this chapter, is the amount which will compensate the party aggrieved for all the detriment proximately caused thereby, or which, in the ordinary course of things, would be likely to result therefrom. No damages can be recovered for a breach of contract, which are not clearly ascertainable in both their nature and origin.