In still water it's best to wait till you feel the fish...then strip/pull set as others have said above...But waiting till you feel the pull of the fish is almost paramount in still water fishing..Does sound from your discription that you had not yet taken up the slack from the cast...

In top water fishing it can take some getting used to, To the waiting to feel... and after a pull set you are still in the strike zone if you do miss the fish and many times you'll find that a fish will turn and slam the fly a second and even a third time..

After seeing that explosive strike at times we all get a bit ahead of ourselves in the first trips out of a new season. I sometimes find I must sort of retrain myself to wait...