Had this one solved in my head and made the first move. But then, after black's reply I realized my planned response was flawed. So, I had to take a few extra seconds to find the correct follow up.
That happens to me in games too. I will work out a combination only to realize part way into it that I overlooked a defensive move. That can be disastrous if I've sacrificed a piece already or created a weakness that will be hard to defend later in the game. I've always been better at strategy than tactics, better at defense than offense, Petrosian style, I guess.