Yeah I wish I could tell you there will come a time when this doesn't happen. It'll get easier once you learn more definitely, but there will ALWAYS be people that don't know how to order their own drink. Youv'e just got to shrug it off my friend, and move on to the next customer.

Some tips/tricks:
A lot of times you (even being new and learning) actually know the menu better than customers. Even ones who seem super confident might have just memorized the way they order and might not actually know what goes into it, etc.
Some things that I had to learn:
-When people order tea, they sometimes order like "venti Earl gray with only one tea bag." Ventis usually have two tea bags, so I usually ring them up for a tall.

-without out fail, people order the SARL as "strawberry acai with no water and with lemonade." Even though there is a way to ring this in as they say, it's not charging them right-- there is a separate button for SARL.

-when people order "grande latte with only one shot," they get pissy if you charge them for a grande latte, and tell me I should only charge them for a tall. Correct way to ring the in is a grande steamed milk ("other" page) with an added shot-- it's more expensive than a tall latte, less expensive than a grande.

-when people want steamed milk over tea bags, its not a regular tea, it's a "custom tea latte". On the same page with the brewed teas.

There are so many more, but in general be confident, you will learn, and try not to use the ask me button until last resort-- there is usually a button for whatever you're trying to communicate!