Do not mistakenly use let for leave. As is true for most words, there are other meanings and nuanced meanings (I’m just going to stick to what is needed for our purposes), but generally, to let means to allow and is often used with the infinitive of a verb; it does not use the -ing form of the verb. To leave means to depart or to allow to remain and is often used with the -ing form of the verb.
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Incorrect: Let it sitting on the stove.
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Correct: Leave it sitting on the stove.
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Incorrect: Leave it sit on the stove.
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Correct: Let it sit on the stove.
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Incorrect: Leave it be.
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Correct: Let it be (just like the old Beatles song).
Sherry
Paul’s book–Literally, the Best Language Book Ever;
Everything Language and Grammar 
Hope this doesn’t sound arrogant but I’m a little surprised at the topics you need to discuss, Sherry. I honestly thought most of these grammar gaffes are obvious to almost all. The only one that I hadn’t known was about stupidest not being a proper word. My son & I always got a kick out of people saying they did a complete 360. We’d smirk & say “I guess they’re back where they started.” I enjoy reading your write-ups about grammar. (Or is write-up not a proper term either?)
Reply: I don’t think that it sounds arrogant at all; however, you might be surprised at how many people search for these kinds of mistakes—we try to do a good mix and keep it light. We’re so glad that you’re enjoying the posts.