The biggest mistake you can make when you are a manager is being indecisive. Of course there are times where you want to be like that, but most of the time there will be bunch of people waiting for you to decide on something. Being decisive is just by itself not gonna be enough. You also need to be able to consistent about your decision. Meaning, just because somebody complained about it without additional input, should not make you change your decision.
On the other hand, sometimes there are cases decision making takes too long. Again there are cases where this is okay, but most of the cases this is not okay either. The thing about human psychology is that there is a certain point where people stop caring. If they expect you to make a decision and you fail on that constantly, they will stop asking you. If they need you to act on something and you dont, they will no longer wait for you to act, instead they will never act and just wait for you to let them know that they can act. God knows when this can be of course.
This over time builds frustration, creates deadlocks and anarchy amongst people while there is no decision maker in place. I know, the current trend is about having autonomous teams, yeah more leadership less management. But I am not saying we need managers. What I am saying is, no matter how hard you try, there will be someone people will be looking to. He/she can be a manager, a teammate, CEO or somebody completely irrelevant. If you are the one people looking up to, then you need to be able to make decisions in order to not let your people down. You need to be able to stand strong, forget about being the nice guy. Because what you are representing is not just yourself, you are also representing the common good for the people around you. When you make a decision you should be able to see almost all possibilities from the perspectives of all that is going to be affected by that decision.
Makings decisions is hard. But not making any kind of decisions and delaying execution for the sake of making people happy is actually harming you and your organisation. Just keep this thing in mind: with every decision you make, there will be at least one person unhappy about it. If you believe in your decision, should you be changing your mind? It is something, you need to “decide”.