Three things that first-time managers wrestle with.
There is no I in team
Even though the above is cliched, it is packed with wisdom.
When you are an individual contributor, it is about you. Your effectiveness is measured by your contributions. Not so when you are a manager. It is no longer about you. Your effectiveness is measured by your team’s output.
This is a radical shift, and you need to internalize this if you want to become an effective manager. You need to shift the focus from yourself to the team and do whatever it takes to make your team effective.
Do not search for yourself in your team
Every member of your team is going to be different with their unique strengths and weakness. Do not seek your reflection in them. You are not seeking friendship; you are after proficient team members. Develop a sense of what makes your team members tick and play to their strengths. If their weakness is debilitating, work on a plan to mitigate that.
Not all glamour and glory
A manager is a representative and spokesperson for their team. Hence, they are in the spotlight. This might give an impression that it is all about glamour and glory. It is not so. There is hard, sometimes tedious work—writing performance reviews, stakeholder management, etc.—going on behind the scenes. If you want to be an effective manager, you have to ace these. If you are addicted to intellectual stimulation, many management tasks might seem dry.
As a manager, you do a lot of behind-the-scenes work. Your team members will not be aware of this. You do not get credit for this. You have to get used to this asymmetry and opaqueness.
Also, from time to time, you will have to give tough feedback to your team. It is not easy. It goes against our nature—we humans shy away from conflict. Giving feedback(both positive and negative) is part and parcel of being a manager. You have to master this art.