I guarantee your enthusiastic happiness with my deliverables. If you’re not happy, you don’t pay and you don’t owe me anything. I’ll apologize for taking up your valuable time.
I’m not charging you for my time and effort. I’m charging you for the value you ask me for. I will not make any promises that money will rain from the sky. What I will promise is my best effort, your enthusiastic happiness, or I won’t charge you. It’s the best I can do.