There are a couple of reasons people might confuse these words. Forego and forgo are both pronounced the same way, and the spelling is incredibly close. Also, some people and dictionaries say forego is just a spelling variation of forgo. The Chicago Manual of Style, however, says to maintain the spelling distinction. Additionally, the words do technically have very different meanings. If you want to be precise in your writing, it would be best to know the correct usage.
Forego: to go before
Forgo: to go without
Their Usage And Some Examples
I love history and studying foregone eras.
“The world always had the same bankrupt look, to foregoing ages as to us.”
-Ralph Waldo Emerson
I decided to forgo dessert so I could get home sooner.
Forego: The meaning hasn’t really changed over the years; though most people will use forego as an alternate spelling of forgo. If you follow the link, you can find out about the term “foregone conclusion,” which seems to be a term Shakespeare coined.
Forgo: This meaning also hasn’t really changed over the years.
If you do choose to use forego as an alternate spelling for forgo, it’s likely no one will notice or consider it an error. However, if you plan to use forego with its meaning of “to go before,” make sure you include the “e.”