I have a couple of thoughts in this area since you're expressing similar concerns as managers I've coached and/or led. You are correct in that every leadership position will require you eventually to make a decision that is unpopular. It comes with the territory. As for your happiness about it, there are a number of factors at play here. The first is the obvious one that you've already identified.
You don't handle being disliked well.
Sometimes as a manager you have to make hard decisions, and they don't always come out the way everyone would like. This will make people disgruntled and unsettled, and that can lead people to disliking you. The problem is that you're addressing this at the wrong time. With every direct report, you have a "credit account" of good will, and you have to deposit into this account every time you can during times when decisions are easy and actions are to everyone's benefit. By establishing a pattern of empathy, concern and good will towards your direct reports, they will trust you to have their best interests at heart even when you have to make a decision against them.
Find out what their needs are, what their goals are, what their dreams are. Do what you can early and often to advance those things. Show them results. Then, during the times when you have to make an unpopular decision, instead of resenting you they'll walk the line with you knowing that you did what you could for them. There's a line in a movie that I use when explaining this to my managers: "When did Noah build the ark? Before the rain."
You aren't acting in accordance to your "value proposition".
As an individual contributor it was simple to realize your value. You did a thing, it benefited the company or a person, and you immediately knew that you'd done a good thing and people appreciated it. You're a manager now. Your value proposition isn't immediate anymore. When you do a thing, it can be weeks or even months before that effect pans out, and by that time no one really knows you did it. You probably don't even recognize that you did it.
You need to start keeping track of the things you do, the decisions you make, the direct reports you help. You also need to start collecting both the "wins" and the "incidents" for your section. Every so often you need to try to correlate the things you do with those wins and incidents. This will help you find the value proposition. If you help a direct report by advocating for a training class to learn a new skill, then 6 months later that skill leads to a promotion. That's a 6 month difference between action and value realization.
I think you're having a "values" crisis.
We are most happy when we're behaving in a manner according to our values that helps us pursue goals. Some questions that I think would be good for you to answer for yourself:
- What are your goals?
- What are you hoping to achieve as a manager?
- Why are you managing people in the first place?
- What are your personal values?
- What do your behaviors say about your personal values (they may not be the same)?
To put it into context, when I became a manager it took a while to realize that my goal was to produce the best software that helps the most people as I could. As an individual contributor I could only do so much of that. As a leader, I can help 5/10/50/100 people do it. My impact can be so much greater. I have to empower and enable people to do it though, so that became my mission. Their goals and their dreams became why I manage people. I can achieve my goal by helping them achieve theirs.
I considered my top 3 values at one point. I thought it was a great exercise. I came up with "integrity", "persistence", and "resourcefulness". These felt right to me. Then a colleague said (out of the blue) as we were discussing it, "I wonder how other people perceive our values." It was such a simple innocent statement, and it hit me like a hammer. It doesn't matter what I think my values are. It matters what my direct reports think my values are.
I polled my team and the final question of the poll was "Based on my behaviors, what do you think are my top 3 values?" I made the choice that I either had to accept what they said or figure out a plan of action to change how they perceived me. They came up with "integrity", "servant leadership", and "faith in us". I'll take that every day of the week, and so I work to make sure those stay the values people perceive of me.
I suggest you figure out what your values are. How do your direct reports perceive your values? If they're different, what are you going to do about it? I think if you're working in accordance with your values it won't matter if you're an individual contributor or a leader. You'll find happiness in what you do.