Sleep on

To sleep on someone means you don’t believe they’ll actually achieve something they said they would or will do. It’s basically someone calling you bluff on something you say you’ll do, but instead of them verbally calling you bluff, they’re thinking it. Its thinking that someone will stay stagnant in a journey, process, career, etc. It’s a lack of respect towards that person either because they haven’t done it before or because you don’t believe in them. Basically, if someone is sleeping on you, you’re not a threat nor respected by that person and this is a time to prove that person wrong.