Bewitched - Season 7 Episode 12

Darrin isn't doing very well creatively and decides to take a vacation. When he returns, he comes up with a sure-fire sales pitch for a very strict client, who rejects him on the spot. Darrin blames his creativity block on Endora and wants Samantha to give him some magic creativity. Samantha gives him a potion that insures great confidence and presents the client with the same rejected idea, which passes. Samantha tells him that his confidence was his own and that the potion was nothing more that soda pop.