Many players have a tendency to think down when serving. The net doesn’t look so high, their racquet is extended overhead and hitting down seems logical to get the ball in the service box.
There’s a big problem with this type of mindset, number one, you’ll hit many serves in the net. Number two; you’re reinforcing a mindset that doesn’t allow you to develop a consistent, reliable serve.
When making contact on the serve most of the time the racquet is straight up or ever so slightly tilted down. When I say ever so slightly tilted down, I mean like one degree tilted down, barely visible to the human eye.