Most often they are expressed with at least a tang of regret. Sometimes the longing is to be able to undo that which was done. Other times the desire is to have acted on that which had been left undone. Regardless, done or undone, it is past tense. You cannot change the past. But how often are we paralyzed by it?
As a leader you are no different from the rest of humanity. You make mistakes. Things do not always work out as planned.
Spoiler alert...you are fallible.
What differentiates the most effective leaders from their peer group is their response to failure. Does your regret sap your confidence, your joy and your passion? Does fear of failure paralyze you from moving forward? Do you dwell on the mistake? Or do you learn from it and use it to motivate you to future success?
Your team chooses to follow you because of the character that you display, day in and day out. They are all realistic enough to know that perfection does not exist, but strength of character does. What will motivate them to continue to follow and support you lies not so much in your ability to be perfect, but rather in your ability to carry on.
When the inevitable happens, acknowledge it, learn from it, and use it to your future advantage. And do it immediately. The longer you wallow in the trough of failure, the longer it will take to reach those fields of success!