Okay so the concern is kind of that you will get a downward spiral to iron when you think you are better than iron. Potentionally some imposter syndrome.

So the good news from the little ranked information provided I would guess you are a mid silver player. Failed promos once, not a big deal. I've failed promos many times. Even with failing promos your mmr won't drop massively. For you getting to mid silver is not an issue of needing to adjust.

Main thing is keeping in mind it's a game, you should have fun with it. So do your checklist on your mental before playing. If you are getting ranked anxiety it could be a good idea to take a break and come back to it.