When facing that decision after missing your first serve, your answer should be to focus on how and where to hit your second serve rather than to focus on not double faulting.  In fact, you are more likely to double fault if you preoccupy yourself with the thought of not double faulting than if you placed your focus on how and where you want to place your second serve.  In acting too, and in life, it is always more productive to focus on doing something rather than to focus on not doing something.  In acting, we call this having a playable action.  In tennis, we might as well call it the same thing.  To illustrate, just think about your serve again.  You can play a kick serve to your opponent's backhand, but you can't play a non-double fault.  It's about pursuing your objectives with specificity.  If your immediate objective in tennis is to pull your opponent off the court with your serve, you can accomplish this by slicing your serve out wide.  On the other hand, if you are just concentrating on not double faulting, you are not pursuing a specific objective or playing an action that has its test in the other person.  In acting, if you're not pursuing a specific objective or playing an action that has its test in the other person, things get boring - because it lowers the stakes and the drama of the scene.  When audience members pay $100 a ticket for a Broadway show or a seat at Arthur Ashe Stadium, they want to see the performer fight to win and not just hope to not lose.  But what the audience thinks is a topic for another blog.  For now, and for yourself, focus on pursuing a positive action rather than on not committing a negative one, and you'll notice a positive improvement in your tennis, your acting, and your life.