Slow everything about your swing down. The thought to keep in mind while at the plate is "I'm just hitting a single". Don't swing for the fences, don't think "I'll pwn these guys", remove all of that.

Simply swing smoothly and easily at the ball, and it will go. Your natural ability will soon take over, your swing will speed up, the timing will improve, and you'll be off to the races.

My first softball league was in college, fresh from years of competitive baseball. My first two swings were both HR's, and at the time of contact I would have sworn they would be singles. My mindset going in was "just make contact and drive the ball". After that, I then tried to hit HR's, and I went games without one. Lot's of pop-ups and foul-balls however. Had to start over with an easy swing.