The major "pitfalls" of a sales job in a retail store have to do with customers and the constant need to sell more merchandise.
On the one hand, customers can always be a problem. They are often unkind to sales staff. They will be in a hurry and be very impatient, or they will need to look through all of your stock and then they will not buy anything after wasting your time. They can be very rude if anything goes wrong.
On the other side of things, there can constant pressure from bosses. They need to sell more merchandise and they will pressure you to get that done. Stores will often do things like tracking how much each of their associates sells and demoting or even firing those who do not sell as much as they should. This will put a great deal of pressure on you to make sure that you are fairly aggressive with the customers. You will then have to find a balance in which you push them hard enough to buy, but not hard enough to make them angry at you.