We all have pet peeves. You know, those little grammatical errors that don't seem to annoy other people, but cause us to grind a measurable amount of enamel off our teeth when we hear them. We hesitate to correct other people because we don't want to be That Pedantic Ass, so we suffer in silence. Except when we're at home alone, and find ourselves shouting at the radio because some NPR reporter who should know better just said "a myriad of something," thereby propagating a widespread grammatical mistake I should not care about, but do.
There are many days I do not reveal myself to be That Pedantic Ass. But not this day.
The word "myriad" is used the same way you would use "many." To clarify: "a myriad of something" is wrong.
You wouldn't say "a many of reasons," right? No. You say many reasons. You say "myriad reasons." As in, there are myriad reasons I should be writing instead of shouting at the radio.