The rights of the parties hereto shall not be prejudiced or restricted by any indulgence or forbearance extended to the other party and no waiver by the parties hereto of any breach of the other party of any of the terms hereunder shall operate as a waiver in respect of any subsequent breach except pursuant to a written instrument signed by the party or parties making such waiver. Any such waiver shall be effective only in the specific instance and for the specific purpose stated in writing.