You must add this clause to your next purchase and sale agreement to avoid uncomfortable situations that threaten your reputation. Most of the time challenges that come up in a transaction are for the most part pretty common. You learn from them and are able to predict if it might happen again in another transaction.
Listen to a story of a recent deal that hammers home why you need to add this clause to all future PSAs. Definitely a lesson learned for all parties, and something I will be adding to my process as a normal course of a transaction.