You need to very weary of people, especially someone who is your direct superior, telling you to slow down. I was in this situation, but luckily used it to my advantage when the time came to leave. They can easily turn around and throw it back in your face, which is what happened to me. Some have suggested waiting 6 months before rocking the boat, but in my experiences, they don’t take kindly to being outperformed, especially when it’s a subordinate. Just quietly leave, and don’t look back. Some situations/companies just aren’t worth working and fighting for.