In multiple lessons, the honorific "お" is used. It is explained briefly as only being added to traditional Japanese words, but I've also heard it explained as being used to indicate that the speaker is directing the question or phrase at you.  I've also noticed that the honorific is not always used, for example:  日本語がお上手ですね！(your Japanese is wonderful!) and あんあたほど上手じゃないです (Not as good as yours). The honorific "お" isn't used in the second sentence. Are both explanations of the honorific correct? and what determines whether it needs to be used or not?

Also, is it still acceptable to not use it at all? I've seen different translations of "I eat sushi" from different websites and some use お and some do not

The second sentence about you would not use it to describe yourself. You can use it to describe others but not yourself.

The context of the situation (formality, difference in social standing) dictates whether the honorific is required or not. When in doubt, use polite language. It's better to be overly polite than to do something considered rude.