This liability can never exceed the amount that the promisor owes under the contract.
The performance of an existing contractual duty owed to the promisor is not good consideration for a fresh promise given by the promisor.
Accordingly, courts will often read implied-in-fact or implied-in-law terms into the contract, placing duties on the promisor.
For what items of damage should the court hold the defaulting promisor?
If it is done at the instance of a third party or without the desire of the promisor, it will not be good considsration.
However, courts will generally imply in law that the promisor must act in good faith and reject the deal only if he is genuinely dissatisfied.
However, promissory estoppel may permanently extinguish the rights of the promisor to claim lump sum after part-payment.
Something that is already done is done, and it does not change the legal position of the promisor.
