If you bite off too much, the reel mower will choke.
A reel mower prefers cutting half the width of the blade or less.
This picture shows the proper position. Follow a line from the middle of the mower to the right corner of the flowerbed. The left of that line is cut grass. The right is uncut grass.
As you mow back and forth, the middle of your mower should follow the cut line.
Do not follow the line made by the wheel. The wheel line is to the right of the cut line. If you follow the wheel line, you will leave strips of grass standing.
If the mower is hard to push, take a smaller bite!