Most Of The Decisions On Your Desk Are Not Yours
Deciding something your team should have decided is expensive twice over, and the second cost is permanent.
Every decision you take that belonged to someone else costs your time, which is recoverable, and their authority, which is not. The second cost compounds. A manager whose call was overturned or pre empted learns something about the boundaries of their role, and adjusts. Next time they bring the question to you earlier, framed more neutrally, with less of their own view attached. Do this often enough and you build an organisation of well briefed messengers, which is exactly the organisation that will overwhelm you and then, when you are stretched thin, fail to catch the thing you needed caught.
The practical test is to ask what would happen if you simply did not answer. If the answer is that a competent person would make a reasonable call and the organisation would survive an imperfect one, the decision is not yours, and the correct response is to say so plainly rather than to answer and hope the pattern does not repeat. Keep a genuinely short list of matters that must come to you, make it explicit, and be willing to be surprised by decisions taken without you as the price of having written it.
This is harder when the person deciding is new, or when the last person in your chair decided everything. Both situations require you to accept a period of worse decisions in exchange for a functioning structure later. Support that period by making your reasoning visible rather than your conclusions: when you do decide something, say what you weighed and why, so that others can decide the next one the way you would have without needing to ask. Reasoning delegates. Answers do not.