The best leaders I've worked with are the ones that know when they should wait and when they should respond immediately. Mature leaders know that some problems go away if ignored for a while. They also know that there are very few times where putting off sending a scathing email or administering a harsh verbal rebuke will give you cause for regret. However, it is pretty frequent that haste to respond to a laden situation will make you wish you had taken more time to think.
There are some situations that call for immediate swift attention. You should strive to identify these situations ahead of time and determine your response in a carefully planned way. This allows you to respond quickly but not be reactive—you've spent the time in prudent though ahead of time so you aren't flying by the seat of your pants.