There are specific times in a client relationship where something changes. These times can cause a client to question everything that they have previously taken for granted and are called Moments of Truth. How you respond as an organisation at these Moments of Truth can have a bit impact on future sales.
As an example, consider a client who has gone through a tender process and and has selected your organisation as their supplier. The moment they sign off on the contract, there is a point of no return, a Moment of Truth. The anticipation and excitement of the imminent project turns to anxiety. Have they made the right decision? What will happen if the project fails? At the same time, their primary Point of Contact with you changes from the sales person to the project manager. How the project manager now communicates will have a magnified impact on the client due to their vulnerability.
Moments of Truth will be different from organisation to organisation but it is important to find them and make sure that the magnified impact is positive not negative.