A decision can be made too quickly, but there is a difference between that and an impulse. A decision can be made to cause, create or prevent a situation of unhappiness.
Sometimes a decision can be made for the best and sometimes it can be made for the worst, although the latter is almost always unintentional. However, sometimes there is a deadly mixture of each component within the decision making process; a decision can be made to distance yourself from a situation that in the long run has an effect on your well-being. At the same time though, there is the possibility you can make a sudden decision, although not always an impulse, and then find yourself in a situation as costly, or more so, to your general happiness.
And with that, a decision as quick as your original one must be made, or in my case, had been made.