Consider whether you might omit from the beginning of any
sentence any single word which is followed by a comma. "Honestly,"
"frankly," "literally," "regardless," and
"actually" are all words that tend to say to the listener,
"Whatever you may have heard before now, disregard it, because I am about
to say something so much more important, truthful, accurate, and
unbiased."
This can have the effect of making one sound pretentious.
However, judicious use of the single word followed by a
comma at the beginning of one's sentences can, indeed, accomplish a desired
effect. It may serve to wake up the listener and alert him that it is time to
start paying attention, because you have been holding out until now with polite
conversation, and you are about to convey the one important idea you want him
to take away from your discussion.