9 times out of 10, delete words (adverbs) that end with “ly” – when trying to convey emotion or writing a description.
Many adverbs end with “ly” as it’s a quick way to turn an adjective into an adverb – “sad” becomes “sadly” and “perfect” becomes “perfectly.”
Unfortunately, it’s also lazy, “describes” rather than “shows” the reader and it affects the rhythm and pace of prose, slowing it down considerably.
EXAMPLE: “I hate you,” she said furiously.
It’s preferable to show an emotion rather than tell the reader how a character feels.
MODIFIED: “I hate you,” she said. Her fingers were rake-like claws.
Of course, there are exceptions to the rule (see considerably above), and it’s down to your own judgement about how much is too much. However, if a quick “ly” search on your would-be bestseller comes up with more “ly”s than you can shake a pen at, it might be time to hit that delete button.