Sounds like maybe you're too hard on yourself? Give yourself time to acclimate. If they pressure you, don't put a wedge between them and you. Smile and say something like, I'm new to retail, getting used to the layout of the store.

It might not hurt, in a few days, to follow this up by asking them for a few secrets of the job. Being able to sell a product means being able to sell YOU... and your confidence. Not a bad thing to learn, either. I wish I had had the opportunity to learn that.