If you do not your customers to re-enter a workflow they have already gone through, add an action at the end of the workflow. An example would be if you did not want the customer to continue receiving emails but instead you wanted to take communication outside of Kolleno e.g. assign to the portfolio "do not call" to avoid customer dissatisfaction.

In this example I have assigned a customer to a portfolio. Here is what options you can choose from to stop the customer from continuing in the workflow.