1.) It can be much more stressful and unpleasant working through other people than being an individual contributor. You must be able to deal with this in a way that doesn't cause too much unhappiness.
2.) You must be a strong distiller of information. You need to be able to understand what information is important and what is not as you will need to distill a very messy situation below you into something coherent to those above you. Developers can often get away with massive detail dumps that lack any sort of narrative. You will not.
3.) Your job is always to make the project successful. You need to have the confidence and leadership ability to make changes as needed on the fly, and explain them in ways so that everyone understands why what is happening is happening.
4.) You must be a strong communicator. You should feel like you are over communicating. I fail here most often, typically you will know it in real time. Do your best to correct it.
5.) You will have more interruptions and starts and stops in your thinking. Organization helps here.
6.) You will go long periods without feeling like you are doing a good job, or feeling like you arent adding anything. You are. Being a manager and a leader is large time periods of being a servant, most often to those below you.
7.) Focus on putting your team in good spots. Find what people are best at, help them excel. Give good people space to grow. Be on the lookout for your next manager below you. Try to help them along and hopefully beyond you.
8.) Large parts of it are just showing up. Asking the dumb questions. Listening. Saying that sounds good, go do it. Holding people accountable. Keep things fun whenever possible.
9.) Largely, it sucks. I do it because I havent found someone else I think could do better for the team yet. If they show up Id gladly get out of it.