"...it is the first principle upon which all Courts of Equity proceed, that if parties who have entered into definite and disctinct terms involving certain legal results — certain penalties or legal forfeiture — afterwards by their own act or with their own consent enter upon a course of negotiation which has the effect of leading one of the parties to suppose that the strict rights arising under the contact will not be enforced, or will be kept in suspense, or held in abeyance, the person who otherwise might have enforced those rights will not be allowed to enforce them where it would be inequitable having regard to the dealings which are thus taken place between the parties."